fixed others very minor bugs.

fixed very minor bugs.

* Some bugs fixed
* Starting enhancements in Libedit: menubar and commands to "plot" current component in PNG or SVF file (SVG file not fully working, must be refined)

* Make USE_WX_ZOOM clipping routine actually clip rather than just test
  if line needs drawn.
* Clean up as many USE_WX_ZOOM #ifdefs as possible.
* Minor coordinate rounding improvements.
* Minor scrolling and panning improvements.
* Remove unused KicadGraphicContext object code.

All: added in popup menus hotkeys info for zoom commands

* Implement code to allow wxDC to handle coordinate conversions between
  device and drawing units.
* Add build settings to enable wxGCDC for wxGraphicsContext testing.
* Remove wxAUI conditional build cruft as it is now required to build
  Kicad.
* Fix scroll increment size regression to prevent jumping around the
  zoom center position.
* Add find GDI+ cmake module for building on WXMSW when wxGraphicsContext
  is enabled.

Added sample gerber files for test (gerbview has problem with 2 files)

Added sample gerber files for test (gerbview has problem with 2 files)

removed global variables and a lot of redundancies

hide/show rastnest in pcbnew is currently not working, will be fixed soon

    * in variable names, change non existent word Hight to High
    * Remove redundant tool in left toolbar (option toolbar)
      (this option is now in layers manager)
    * Show layers in horizontal combo box in same order as in layer manager.
++all:
    minor code cleaning.

* Remove redundant background redrawing RedrawActiveWindow.
* Remove redundant managed cursor callback in RedrawActiveWindow.
* Use refresh to redraw instead of directly calling RedrawActiveWindow.
* Remove unused SetDrawBgColor for drawframe.cpp.
* Fix compiler warning in cvpcb/cvframe.cpp.
* Fix menu spelling and syntax errors in pcbnew.
* Rename Trace_Curseur to DrawCursor in common/drawpanel.cpp.

Code cleaning.
Patch for 3D problem with macOSX

Added patch for macOSX
turn on fast algo for draw grid (should work now)

* Fix debug asserts when passing NULL pointers to wxAuiPaneInfo.
* Fix Kicad main window sash sizer bug when using wxAui.
* Remove specctra_test from Visual Studio builds to prevent build errors.
* Add WIN32 to layer widget test so it will build properly on Visual Studio.
* Fixed compiler conversion warnings in PCBNew.
* Fixed worksheet print scaling in PCBNew.
* Minor code renaming.

Code cleaning and using DrawPanel->Refresh() instead of ReDraw() when possible.