gst/gstinfo.*: Change name parameter of _gst_debug_register_funcptr to const to reflect the constness of its use in t...

Original commit message from CVS:
* gst/gstinfo.c:
* gst/gstinfo.h:
Change name parameter of _gst_debug_register_funcptr to const
to reflect the constness of its use in the function as well
as to quiet a gcc warning.