Compilation error when using mingw+scons

Error was caused by boost library (which doesn't seem to be working with Cycles too
when compiling with mingw). Switched mingw to use TR1 unordered collections. Also,
there was re-declaration of strcasecmp when mingw is used.

Additional changes are related on using own process spawning when BF_TOOLSET is set to
mingw. Seems to be working fine now (i've got too long command line error) and no
warning are supressing now (as it was told in comment for commented own process spawning).

SConstruct

@@ -147,9 +147,8 @@ if toolset:
         env.Tool('mstoolkit', [toolpath])
     else:
         env = BlenderEnvironment(tools=[toolset], ENV = os.environ)
-        # xxx commented out, as was supressing warnings under mingw..
-        #if env:
-        #    btools.SetupSpawn(env)
+        if env:
+            btools.SetupSpawn(env)
 else:
     if bitness==64 and platform=='win32':
         env = BlenderEnvironment(ENV = os.environ, MSVS_ARCH='amd64')