Tidied up event handlers.

Moved switching canvas routines to pcbnew, as they are used only there right now (otherwise libgal would have to be linked to every Kicad application).

Added missing callback function (combine callback).

Removed DRAW_MODE_NORMAL, DRAW_MODE_PREPARE_EDGES, DRAW_MODE_DRAW_EDGES modes.

Fixed layer picker for exporting to pcbnew
Realigned pcb layer name with class BOARD

Dynamic contrast for netname and pin numbers ('halo' text)
Handle netname drawing even on diagonal tracks

More layer classification cleanup

Modified CMakeLists.txt in order to compile Kicad with KICAD_GAL=ON for Windows

Added settings that allow to use M cross environment (http://mxe.cc) to crosscompile Kicad for Windows.

bit string version of property_tree. The ram resident structure of the ptree is
mostly compatible with one created using the xml_parser from
boost::property_tree, with slight differences in the way atoms are stored. The
result is you can use Format() to convert from xml to s-expression, but not the
other way around. You can write a simple s-expression beautifier in just a few
lines of code.

The main value however is the s-expression parser, i.e. Scan(), which is an
alternative to crafting a custom recursive descent parser for a particular
grammar. The tipping point depends on whether you want to read only a small
portion of a much larger document. If so, then using the ptree will likely be a
"faster to code" route. Documentation on how to navigate a ptree can be found on
the boost website and there are a number of examples in the
pcbnew/eagle_plugin.cpp file in this project. Powerful path navigation support
makes it easy to extract a subset of a ptree.