Adds support for utf paths on Windows.

Not all file formats/calls are supported yet. It will be expended.

Please from now on use BLI_fopen, BLI_* for file manipulations.
For non-windows systems BLI_fopen just calls fopen.
For Windows, the utf-8 string is translated to utf-16 string in order to call UTF version of the function.

build_files/scons/tools/Blender.py

@@ -340,6 +340,7 @@ def creator(env):
 
     if env['OURPLATFORM'] in ('win32-vc', 'win32-mingw', 'linuxcross', 'win64-vc'):
         incs.append(env['BF_PTHREADS_INC'])
+        incs.append('#/intern/utfconv')
 
     env.Append(CPPDEFINES=defs)
     env.Append(CPPPATH=incs)