UI: fix uitest for VMS

- On VMS, apps/apps.c depends on apps/vms_term_sock.c, so add it to
  the build
- On VMS, apps/*.c are compiled with default symbol settings,
  i.e. uppercased and truncated symbols, which differs from test
  programs.  Make sure uitest.c knows that with a few pragmas.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2218)