3D viewer: fix incorrect scaling factor when using nanometers.
Very minor other fixes

Fix some comments.  Enhance LEGACY_PLUGIN such that it can tolerate, then fix bad legacy footprint libraries containing duplicate footprint names.
This may have been an undocumented bug from more than a year ago, which manifested itself in *.mod files containing duplicate names.
LEGACY_PLUGIN loads those now quietly, but appends "_v2", "_v3", etc. to each succeeding duplicate sharing the same name.

base on expected text and current window font.

Expand the virtual world to 2.14 meters in the nanometer build of PCBNEW.
This seems to be holding up for now.

Delete LEGACY_PLUGIN cache after deleting library of same name.
Remove automatically generted freerouter help header.
Add Normalize() to BOX2.
Clamp some values in the virtual space of drawframe.cpp

Should allow Pcbnew code easier to change and Gerbview code more understandable and easier to maintain.
Code cleaning (remove dead code, add comments).
Minor other enhancements.

Add patch from Lorenzo Marcantonio. Fix some warning issues, and zlib issue under Windows (zlib sources added)

All: change MILS_TO_IU_SCALING_FACTOR constant to IU_PER_MILS ( and MM_TO_IU_SCALING_FACTOR to IU_PER_MM)
Also fix bug 985654.

All: change MILS_TO_IU_SCALING_FACTOR constant to MILS_PER_IU  ( and  MM_TO_IU_SCALING_FACTOR to MM_PER_IU)
Also fix bug 985654.

Other scaling factors (MILS_TO_IU_SCALING_FACTOR and DECIMILS_TO_IU_SCALING_FACTOR)
also defined only in convert_to_biu.h.
Allows different scaling value for Gerbview.
Needs more tests.

solution to see that it was not pre-computing constants when used in static initializers.

So we have two use cases, and need two solutions to be optimal, since the compiler 
is too stupid to do the right thing.

I think we need something else for compile time computable constants, to be optimal 
in both use cases.  There is quite a bit of code savings by using a macro for that 
situation from my testing.  To fully capitalize on this, we need to go back and make 
Mm2mils() and what not macros also, or have MACRO versions of them too.

  as a starting point
* Make double Distance() take double arguments and remove internal range checking.
* Start on EDA_DRAW_FRAME::AdjustScrollBars() and use "double" for most all calculations
  in anticipation of setting INT_MAX INT_MIN limits eventually.

* Move board item object Format() functions into PCB_IO object.
* Change file format to use layer names instead of numbers.
* Change file extension to kicad_pcb.

// This provides better project control over rounding to int from double
// than wxRound() did.  This scheme provides better logging in Debug builds
// and it provides for compile time calculation of constants.


#include <stdio.h>
#include <assert.h>
#include <limits.h>

//-----<KiROUND KIT>------------------------------------------------------------

/**
 * KiROUND
 * rounds a floating point number to an int using
 * "round halfway cases away from zero".
 * In Debug build an assert fires if will not fit into an int.
 */

#if defined( DEBUG )

// DEBUG: a macro to capture line and file, then calls this inline

static inline int KiRound( double v, int line, const char* filename )
{
    v = v < 0 ? v - 0.5 : v + 0.5;
    if( v > INT_MAX + 0.5 )
    {
        printf( "%s: in file %s on line %d, val: %.16g too ' > 0 ' for int\n", __FUNCTION__, filename, line, v );
    }
    else if( v < INT_MIN - 0.5 )
    {
        printf( "%s: in file %s on line %d, val: %.16g too ' < 0 ' for int\n", __FUNCTION__, filename, line, v );
    }
    return int( v );
}

#define KiROUND( v )    KiRound( v, __LINE__, __FILE__ )

#else

// RELEASE: a macro so compile can pre-compute constants.

#define KiROUND( v )  int( (v) < 0 ? (v) - 0.5 : (v) + 0.5 )

#endif


//-----</KiROUND KIT>-----------------------------------------------------------

// Only a macro is compile time calculated, an inline function causes a static constructor
// in a situation like this.
// Therefore the Release build is best done with a MACRO not an inline function.
int Computed = KiROUND( 14.3 * 8 );


int main( int argc, char** argv )
{
    for( double d = double(INT_MAX)-1;  d < double(INT_MAX)+8;  d += 2.0 )
    {
        int i = KiROUND( d );

        printf( "t: %d  %.16g\n", i, d );
    }

    return 0;
}

* Remove internal units from BASE_SCREEN and it's derivatives.
* Remove internal units from EDA_DRAW_FRAME and it's derivatives.
* Use build time code to replace internal units conversions.
* Fix scaling bug in page layout sample window that I created in my
  last commit.

* Move all convert from user to internal units into base_units.cpp.
* Remove internal units parameters from all moved conversion functions.
* Revise all source code that calls the moved conversion functions.
* Remove internal units from all dialog text control helper classes.

* Scale page reference border and title block, grid sizes, and zoom factors
  correctly for nanometers.

Other minor fixes.

* Move all convert from internal to user units functions into separate file.
* Remove internal units parameter from all moved conversion functions.
* Revise all source code that calls the moved conversion functions.
* Compile these conversion routines separately for the appropriate pcb or
  schematic internal units.
* Move internal units specific status bar update code into the appropriate
  application for updating the status bar.
* Move millimeter user units rounding function to common.cpp.

* Move EDA_TEXT object into separate header and source file.
* Compile EDA_TEXT class separately for BOARD_ITEM and SCH_ITEM units.
* Compile PAGE_INFO  class separately for BOARD_ITEM and SCH_ITEM units.
* Minor formatting tweaks to Pcbnew s-expression file.
* Move internal unit formatting functions into BOARD_ITEM and SCH_ITEM.

If enable in preference menu, allow the pan with drag mouse with middle button down.
both unlimited and limited pan is allowed.

Some minor code cleaning.

Enhancements in AddMenuItem (that accepts now a menu type)
Partial use of the Edwin van den Oetelaar's patch (patch not fully working or correct)

Instrument saveNETCLASS() with fmtBIU().
Can now round trip to mm board file using LEGACY_PLUGIN in DEBUG build.

* Save dialog now supports saving boards to new file format.
* Add CMake option to build s-expression file save.
* Add check to main CMakeList.txt file to make sure nanometers are
  enables when the new file format is built.
* Minor tweaks to object format functions for improved output.
* Rename kicad_plugin.h/cpp to legacy_plugin.h/cpp.