gst/qtdemux/qtdemux.c: Use GST_WARNING instead of GST_ERROR for all the too short/long atoms when parsing.

Original commit message from CVS:
* gst/qtdemux/qtdemux.c: (qtdemux_parse), (qtdemux_parse_trak):
Use GST_WARNING instead of GST_ERROR for all the too short/long atoms
when parsing.
Also let's be a bit less vulgar in our warning messages :)