VMS: turn on name mangling for all our programs

With the change to have separate object files by intent, VMS name
mangling gets done differently.  While we previously had that for
libraries only, we must now turn that on generally for our programs,
because some of them depend in internal libraries where mangled names
are all that there is.

Dynamic modules are still built with non-mangled names, which is good
enough to show that it's possible to build with our public libraries
using our public headers.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7208)