BuildSystem: Detect external library Lua in version 5.3.

On some platforms, you decide to go for one specific version of Lua, for
example in OpenBSD. On other platforms, you are able to install several versions
side-by-side, for example in Ubuntu and Fedora. Asterisk already works with
Lua 5.3. Asterisk failed to detect Lua 5.3 on those platforms which allow
several versions.

ASTERISK-27592

Change-Id: If7a4b395d844a464e9a1f4f626c5bff4ee67eed8