MFC r256060,r256650: kldxref: Do not depend on the directory order.

Sort the filenames to get a consistent result between machines of the same
architecture.

Also, sort FTS_D entries after other entries so kldxref -R works properly in
the uncommon case that a directory contains both subdirectories and modules.
Previously, this may have happened to work, depending on the order of files
in the directory.

PR:		bin/182098
Submitted by:	Derek Schrock (original version)
Tested by:	Derek Schrock
MFC r259521:
Do not allow O_EXEC opens for fifo, return EINVAL.
[automated] Merge in upstream-github/stable/9