Pcbnew: fix crash after displaying "The text thickness is too large for the text size. It will be clamped" when editing pcb text properties (Linux specfic)

Other very minor changes.

soldermask. Nevertheless, it would be nice to have proper gerbers to
begin with, i.e., gerbers with no silkscreen in soldermaskless areas.
Of course, most of the problem can be taken care of by drawing the
footprints properly. However, sometimes the silkscreen of one
footprint ends up on the pads of another one (think components under a
so-dimm card, for example). The attached patch adds an option to
subtract the soldermask from the silkscreen when doing gerber output.

marco

Cosmetic enhancements. Eeschema: in libedit the Value Field is n more editable in the field editor dialog (due to recent changes in library code)

Pcbnew: For zone filling algo, change the default polygon library from Kbool to Boost::polygon (USE_BOOST_POLYGON_LIBRARY default is ON). (need to rebuild makefile)
Gerbview: added decimal format for coordinates, sometimes found in Gerber files.

Gerbview: Added support for complex definitions of parameters (like $3=$2+5/2) in aperture macros and primitives macro.

Gerbview:  Added support for complex definitions of parameters (like $3=$2+5/2)  in aperture macros and primitives macro.

Pcbnew: fix a bug in filling zone algo, only when using boost::polygon. Gerbview: preparing enhancements.

minor cleanup. minor enhancements. Finish file housekeeping. add Bug 682586 fix from Mark van Doesburg.

Pcbnew: code cleaning, dialogs converted from Dialogblocks to wxFormBuilder, file housekeeping. Add patch from Manveru.

Fix a bug that crashes Pcbnew when closing Freeroute dialog ( Only happens with wxWidgets 2.9.1, but this was a bug)

pcbnew and directs gerber/hpgl etc. output into that directory.
There's a browse button that opens a dialog for browsing. If the
directory does not exist, it is created. Tested in linux, not in
windows. Wxwidgets methods are used for file (name) manipulations, so
things are probably ok in windows, too.

marco