Use audioconvert for converting from non-native endianness floats in auparse instead...

Use audioconvert for converting from non-native endianness floats in auparse instead of doing it ourself. Fixes #424527.

Original commit message from CVS:
Patch by: René Stadler <mail at renestadler dot de>
* configure.ac:
* gst/auparse/gstauparse.c: (gst_au_parse_reset),
(gst_au_parse_parse_header), (gst_au_parse_chain):
* gst/auparse/gstauparse.h:
Use audioconvert for converting from non-native endianness floats
in auparse instead of doing it ourself. Fixes #424527.
This needs the audioconvert from plugins-base CVS.