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.

source/blender/src/writeavicodec.c

@@ -37,7 +37,7 @@
 #include <config.h>
 #endif
 
-#ifdef _WIN32
+#if defined(_WIN32) && !defined(FREE_WINDOWS)
 
 #define  INC_OLE2
 #include <windows.h>