src/Versions.in: Add guards for opt. alisp symbols

src/Versions.in: Add guards for opt. alisp symbols

Add guards for optional alisp symbols. This ensures that the Versions
file does not contain undefined symbols when building alisp support is
disabled.

Fixes Gentoo bugs 914511 (https://bugs.gentoo.org/914511),
    914643 (https://bugs.gentoo.org/914643),
    and 919417 (https://bugs.gentoo.org/919417).

Fixes bug #305
Fixes alsa_lisp symbol error reported in bug #356

Closes: https://github.com/alsa-project/alsa-lib/pull/376
Fixes: https://github.com/alsa-project/alsa-lib/issues/305
Link: https://github.com/alsa-project/alsa-lib/issues/356
Signed-off-by: Nicholas Vinson <nvinson234@gmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>