Initial libjit skeleton.

Not currently generating instructions, but most of the flow is right up to
that point. A lot of work required to refactor the emitter, but wanted to
get this checked in.

xenia-build.py

@@ -300,7 +300,7 @@ def run_gyp(format):
       '-f %s' % (format),
       # Set the VS version.
       # TODO(benvanik): allow user to set?
-      '-G msvs_version=2010',
+      '-G msvs_version=2012e',
       # Removes the out/ from ninja builds.
       '-G output_dir=.',
       '--depth=.',