gen-casefold-txt.pl and gen-casemap-txt.pl are licensed under GPLv2+, so
they are not touched by this commit.
A lot of *.c files in tests/ don't have a license header.
https://bugzilla.gnome.org/show_bug.cgi?id=776504
After this patch, there is but one remaining use of g_thread_init(),
which is in tests/slice-threadinit.c, a testcase dedicated to testing
the functionality of gslice across a g_thread_init() boundary.
This testcase is pretty meaningless these days... probably we should
delete it.
Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().
Remove those uses, as they are no longer required.
https://bugzilla.gnome.org/show_bug.cgi?id=686161
