Configure: Tidy up AC_CHECK_FUNCS

Move all of our AC_CHECK_FUNCS calls into a single, ordered, list
so that it's easier to see what's being checked for and what's not.

Reviewed-on: http://gerrit.openafs.org/2598
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 3fc5863f062c14c346bcc50c82b8d15971750e55)

Change-Id: I167b42d84c9ddbb8b35aee6b4ced3c7a809e72dc
Reviewed-on: http://gerrit.openafs.org/9423
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>