Build System: Fixes for configure script.

* Replace all 'else if' statements with 'elif'.
* Use loop to detect versioned lua headers and libraries.

The loop for detecting lua fixes a bug where LUA_INCLUDE would be
appended with the directory of every lua version after the first one is
found.

Change-Id: I3276f9aee955014108345be6092f51c932b43a0f