API: add gst_plugin_register_static() and deprecate

API: add gst_plugin_register_static() and deprecate

Original commit message from CVS:
* docs/gst/gstreamer-sections.txt:
* gst/gst.c: (init_post):
* gst/gstplugin.c: (_gst_plugin_register_static),
(gst_plugin_register_static), (_gst_plugin_initialize),
(gst_plugin_register_func):
* gst/gstplugin.h: (GST_PLUGIN_DEFINE_STATIC):
API: add gst_plugin_register_static() and deprecate
GST_PLUGIN_DEFINE_STATIC, since it's not portable
(#498924).
Also, in _gst_plugin_register_static(), make sure to call
g_thread_init() before calling GLib functions such as
g_list_append() if we're not initialised yet, since that
may lead to random crashes with older GSlice/GLib versions.
* tests/check/gst/gstplugin.c:
Adapt unit test to above changes.