libs/gst/base/gsttypefindhelper.c: Fix off-by-one bug that would only allow peeks...

libs/gst/base/gsttypefindhelper.c: Fix off-by-one bug that would only allow peeks of N-1 bytes from the start even if...

Original commit message from CVS:
* libs/gst/base/gsttypefindhelper.c: (buf_helper_find_peek):
Fix off-by-one bug that would only allow peeks of N-1 bytes
from the start even if the buffer to typefind on contains
in fact N bytes of data (makes vorbis typefinding from a
vorbis identification header buffer work).
* tests/check/Makefile.am:
* tests/check/libs/.cvsignore:
* tests/check/libs/typefindhelper.c: (GST_START_TEST),
(gst_typefindhelper_suite), (main), (foobar_typefind),
(plugin_init):
Add very basic unit test for gst_type_find_helper_for_buffer()
that checks for the problem fixed above.