rustc: 1.2.0 -> 1.3.0
rustcMaster: 2015-09-05 -> 2015-09-21
This also removes the llvm bundling which reduced immediate the closure size
by ~50MB. It also tries to reduce some of the superfluous dependencies
to help reduce the number of potential rebuilds (namely removing git).
This reduces rustc's size from 359 MiB to 186 MiB.
Maybe we should disable doc generation altogether, since it's very
slow and people who need docs will JFGI anyway. But for now I've left
it.
