GObject: Remove more leftover markup from headers
gio tests: add codegen to BUILT_SOURCES

We need to have these in BUILT_SOURCES so that 'make' knows to generate them
before attempting to compile other .c files in the same directory (since some
of these files include the header).

Should fix up remaining issues about partial versions of this file being
included under parallel builds.

https://bugzilla.gnome.org/show_bug.cgi?id=725891
Updated Chinese (China) translation
Updated Latvian translation
gtype – Mark _get_instance_private() function as G_GNUC_UNUSED

clang likes to complain about it being unused.

https://bugzilla.gnome.org/show_bug.cgi?id=723899