Fix -Wtypedef-redefinition warning for locale_t.

xlocale.h doesn't do much more than defining locale_t, so there's no
harm in just including it directly.

Change-Id: I47dccdc3d35bbee6b59cccfbf3a1c508e795c913
Merge pull request #16 from awong-dev/fixwarn

Fix -Wtypedef-redefinition warning for locale_t.