Fixes nasty bug where some parts of the code didn't define WIN32_THREADS
and were using the integer mutex implementation, causing even confusion
to the debuggers.
And there is little interest of other thread implemenation on Win32
besides Win32 threads.
Use scons target and dependency system instead of ad-hoc options.
Now is simply a matter of naming what to build. For example:
scons libgl-xlib
scons libgl-gdi
scons graw-progs
scons llvmpipe
and so on. And there is also the possibility of scepcified subdirs, e.g.
scons src/gallium/drivers
If nothing is specified then everything will be build.
There might be some rough corners over the next days. Please bare with me.
Specifically, move all or most of
glapi/glapi.c to mapi/u_current.c,
glapi/glapi_execmem.c to mapi/u_execmem.c,
glapi/glthread.[ch] to mapi/u_thread.[ch]
and remove their dependencies on core Mesa headers.
