plugins/elements/gstfilesrc.c: If not using mmap'ed files try to seek to the end...

plugins/elements/gstfilesrc.c: If not using mmap'ed files try to seek to the end instead of the start to determine wh...

Original commit message from CVS:
Patch by: Jindrich Makovicka <jindrich.makovick at itonis dot tv>
* plugins/elements/gstfilesrc.c: (gst_file_src_start):
If not using mmap'ed files try to seek to the end instead of the
start to determine whether we can seek at all. This fixes the case
of 2GB+ files over NFS, where seeks in the first 2GB can succeed but
seeks for everything afterwards fail. Fixes #400656