gst/parse/: Reverted previous patch as it required to bump the flex dependency to 2.5.31, where fc4/5 seem to ship on...

Original commit message from CVS:
* gst/parse/Makefile.am:
* gst/parse/grammar.y:
* gst/parse/parse.l:
Reverted previous patch as it required to bump the flex dependency to
2.5.31, where fc4/5 seem to ship only the ancient 2.5.4a :(