plugins/elements/: Use gst_buffer_try_new_and_alloc() and handle errors instead of...

plugins/elements/: Use gst_buffer_try_new_and_alloc() and handle errors instead of using gst_buffer_new_and_alloc() w...

Original commit message from CVS:
* plugins/elements/gstfdsrc.c: (gst_fd_src_create):
* plugins/elements/gstfilesrc.c: (gst_file_src_create_read):
Use gst_buffer_try_new_and_alloc() and handle errors instead of
using gst_buffer_new_and_alloc() which aborts if the buffer couldn't
be allocated.