Merge pull request #117 from Unity-Technologies/monoclass-userdata

add support for storing custom data on a MonoClass, so Unity can store c...
Conflicts:
	msvc/mono.def
Wrap g_free with mono_unity_g_free rather than exporting it directly to avoid symbol conflicts on Windows.

Conflicts:

	msvc/mono.def
	unity/unity_utils.c
	unity/unity_utils.h

Conflicts:
	unity/unity_utils.h
Expose things unity uses.
Make DefaultSurrogateSelector public for now.
Update build scripts.