Convert to fractional framerates.

Convert to fractional framerates.

Original commit message from CVS:
* ext/aalib/gstaasink.c: (gst_aasink_fixate):
* gst/debug/gstnavigationtest.c:
(gst_navigationtest_handle_src_event):
* gst/videofilter/gstvideofilter.c:
(gst_videofilter_format_get_structure), (gst_videofilter_setcaps),
(gst_videofilter_init):
* gst/videofilter/gstvideofilter.h:
Convert to fractional framerates.