[Gtkradiant] trunk now building on win32

[Timothee Besset]

Patched some stuff on trunk for win32:

   - removed libxml2 from tree, use a seperate libxml2/ directory next to 
GtkRadiant/ for win32
   libxml2 will be distributed seperately as an archive based on official 
release (same as win32 Gtk SDK)
   (check on zerowing for the latest archive)
   libxml2 is now used as dynamic shared object on win32, makes sense since 
many module will rely on it
   - cleaned q3map, removed GL dependencies
   - updated Debug and Release builds on win32, it compiles and runs now