Support for building bf-blender under windows with gcc (huge thanks to

Florian Eggenburger).

Full instructions are in doc/README.windows-gcc.

Main differences from Florian's patch:

- the 'lib' dir should now be the same level as the 'blender' dir (rather
than being a subdir of 'blender'). This is consistent with the other
platforms that bf-blender supports (tuhopuu will also adopt this convention
hopefully soon).

- the script 'free_windows-env.mk' is no longer needed ... see the
docs about how this is overcome (again, tuhopuu will hopefully
also follow this route soon).

- the dlltool dir has it's own Makefile that builds all of the
needed stub libraries from the dll's in cvs.

intern/SoundSystem/SND_DependKludge.h

@@ -34,7 +34,7 @@
  * ***** END GPL/BL DUAL LICENSE BLOCK *****
  */
 
-#if defined (_WIN32)
+#  if defined (_WIN32) && !defined(FREE_WINDOWS)
 #define USE_OPENAL
 #elif defined (__linux__)
 #	if defined (__i386__)