gst/: Maintain API and ABI when --disable-parse is used. Now that we have an appropri...

gst/: Maintain API and ABI when --disable-parse is used. Now that we have an appropriate error code, we can just retu...

Original commit message from CVS:
Based on patch by: Peter Kjellerstedt  <pkj at axis com>
* gst/Makefile.am:
* gst/gstparse.c: (gst_parse_launchv), (gst_parse_launch):
* gst/gstparse.h:
* gst/gstutils.c: (gst_parse_bin_from_description):
* gst/gstutils.h:
Maintain API and ABI when --disable-parse is used. Now that
we have an appropriate error code, we can just return NULL and the
appropriate error when gst_parse_launch() is used despite it having
been disabled (#342564).
* tests/check/Makefile.am:
* tests/check/pipelines/.cvsignore:
* tests/check/pipelines/parse-disabled.c:
Make sure these functions exist and return NULL plus a GError when
--disable-parse is used.