Remove call to deprecated g_thread_init()

The documentation for glib says: "g_thread_init has been deprecated
since version 2.32 and should not be used in newly-written code. This
function is no longer necessary. The GLib threading system is
automatically initialized at the start of your program."

[dsme] Remove call to deprecated g_thread_init()
Require glib2 >= 2.32.0 since g_thread_init() call is omitted
Merge pull request #56 from spiiroin/fix_deprecated

Remove call to deprecated g_thread_init()