Remove the cmake test for gcc-4.4

It tests for gcc, and conky is perfectly capable of being compiled with e.g. clang.
Fix compilation with clang
Fix an some strange code found by a clang warning
Add support for lua 5.2

luamm is now able to be compiled with both lua 5.1 and 5.2 (assuming 5.2 has backward
compatibility features compiled in). It is my intention to always support at least two versions
of lua.
Merge remote-tracking branch 'upstream/master'