autoconf: attribute type checks
Check for function attributes by type and update src/afs/stds.h to
conditionally include the attributes detected, instead of checking for
specific compilers and compiler versions.
This allows attributes to be used when building under Solaris Studio.
Change-Id: I8a4dbc1b2cb6032d28176349481085bf6deb309c
Reviewed-on: https://gerrit.openafs.org/12963
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>