Improve shared library building support

Improve shared library building support

This change removes the need to maintain two forms of symbol export
lists, instead generating the simpler lists required by AIX and Mac OS X
from the more complex Linux and Solaris mapfile. It can only handle
simple mapfiles at present, any more complex files (for example, those
which contain versioning information) will require changes to the
translation script. The now unused .exp files are removed, and a
dependency on the .map file added to the library build line.

This change adds support for export lists to Darwin for the first time.
Doing so identified a number of symbols in libafsrpc that are required
by libafsauthent, which were not being exported. Export these symbols,
and bump the minor revision of the shared library.

Change-Id: Ibd1d02bb89b85500dc2a010e6cde1f4b81efe050
Reviewed-on: http://gerrit.openafs.org/1831
Reviewed-by: Russ Allbery <rra@stanford.edu>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>