The file used by Debian is lua5.1.pc (corresponding to the library name), and it's correctly in the -dev package.
The lua.pc you refer to is upstream's example in the doc tree. Again, see README.Debian.gz for why the library name includes the version number. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org