This is required to avoid name conflicts with the Cocoa libraries
on OS X.
I renamed the `class SolveSpace` to `class SolveSpaceUI`, because
that's what it does, and because otherwise the namespace would
have to be called something else than `namespace SolveSpace`.
However, don't use ssglLineWidth for UI drawing operations.
These only draw horizontal or vertical lines that don't need to
be antialiased, and thus don't require the workaround. In fact
the workaround would make them thicker than needed.
Microsoft defines an RGB() macro that at one point was compatible with our
version (returning a packed integer containing 8-bit red, green and blue
channels), but is no longer, and the incompatibility led to an awkward
situation in w32main.cpp where we had to restore Microsoft's form of the
macro in order for the commctrl.h header to compile. By renaming the macro
to RGBi()---analogous to the RGBf() macro we already define---we avoid the
hassle entirely.
The SolveSpace top-level directory was getting a bit cluttered, so
following the example of numerous other free-software projects, we move the
main application source into a subdirectory and adjust the build systems
accordingly.
Also, got rid of the obj/ directory in favor of creating it on the fly in
Makefile.msvc.
