util/mkdef.pl: Produce version scripts from unversioned symbols

This allows setting up export maps for DSOs as well in a uniform way.
This also means that util/mkdef.pl no longer picks up the target
version from configdata.pm, and it has to be given on the command line
instead.  This may be used to give modules separate versions as well,
if desirable.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7347)