Improve libroken configure check

It is not sufficient to just check if libroken is available; we need
to check if the specific functionality we want is there. So, try to
compile and link while referencing specific functions.

As mentioned in the comments, testing every single function we use may
not be practical, and we should perhaps just add functions to test as
we find breakage. This commit tests rk_rename, which is missing in at
least the Debian package heimdal-dev, version
1.4.0~git20100726.dfsg.1-2+squeeze1.

Change-Id: I0ac6c9aea1f8598bb1b1315544683b2403de5f69
Reviewed-on: http://gerrit.openafs.org/8916
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>