Add autoconf-archive to src/external
Add autoconf-archive to the src/external mechanism, so we can more
easily import and update the AX_* m4 macros we pull in from
autoconf-archive. Commits are imported from
<git://git.savannah.gnu.org/autoconf-archive.git>.
We already have a copy of ax_gcc_func_attribute.m4 in the tree, so
include that in the list of files. While we're here, also include a
few more macros for checking compiler flags, which will be used in
subsequent commits.
Change-Id: I8c6288fc1d48a47837ca08f8b9207e0ada921af8
Reviewed-on: https://gerrit.openafs.org/14133
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>