Add files containing the export lists used on UNIX, in each directory

Add files containing the export lists used on UNIX, in each directory
where we build a shared library, whether or not it gets installed.
These should match the complete AIX export lists for a full build
including krb4 support, and will eventually be used on other UNIX
platforms, and cut down to just the symbols we actually want to
export.

We'll also have to add additional information, eventually, for
versioning and such, but currently this is just a list of C symbol
names.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@16259 dc483132-0cff-0310-8789-dd5450dbe970