Check the export lists against the newly built shared library to make sure all

Check the export lists against the newly built shared library to make sure all
the symbols we want to export are actually defined.  GNU/Linux only, for the
moment, but it ought to work on any system using the GNU version of nm, and not
too hard to modify for other ways of extracting the exported symbols of a
library.

* util/export-check.pl: New file.
* config/shlib.conf (*-*-linux*): Run export-check.pl after building a shared
library.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@17609 dc483132-0cff-0310-8789-dd5450dbe970