Generate aclocal-m4-deps.mk more deterministically and portably.

Generate aclocal-m4-deps.mk more deterministically and portably.

Sort the list of files generated by find to make the order of the
entries deterministic.  When sorting, use explicit "C" collation.  Use
an explicit tab character instead of '\t' as some sed implementations
treat '\t' as an escaped 't' instead of a tab.

gdb/ChangeLog:

	* gnulib/aclocal-m4-deps.mk: New file.
	* gnulib/update-gnulib.sh: Generate "aclocal-m4-deps.mk"
	deterministically.