Backport r1706533 to 2.4: Turn 5.1/5.2 order upside down, simplify. This...

Backport r1706533 to 2.4: Turn 5.1/5.2 order upside down, simplify. This should also (AFAIK) work with Ubuntu/Debian, which has previously been known to fail to compile mod_lua.so

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1706534 13f79535-47bb-0310-9956-ffa450edef68