plugins/: Use #ifdef for HAVE_XYZ for consistency.

plugins/: Use #ifdef for HAVE_XYZ for consistency.

Original commit message from CVS:
* plugins/elements/gstelements.c:
* plugins/elements/gstfilesink.c: (gst_file_sink_do_seek),
(gst_file_sink_get_current_offset):
* plugins/indexers/gstindexers.c: (plugin_init):
Use #ifdef for HAVE_XYZ for consistency.
* tests/check/Makefile.am:
* tests/check/elements/.cvsignore:
* tests/check/elements/filesink.c: (setup_filesink),
(cleanup_filesink), (GST_START_TEST), (filesink_suite):
Add some unit tests for filesink.