Valid build script for 1.6.4

PR does two things:

1) Mojang re-released 1.6.4 without updating the version number; this broke the bundled Forge md5 hashes of said releases: http://terrafirmacraft.com/f/topic/5295-compiling-forge-965/

2) You are pulling down "master" from PCC. You should be pulling down a version that is compatible with 1.6.4.