rustc: Update both versions of the compiler

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).

pkgs/development/libraries/jemalloc/default.nix

@@ -8,6 +8,11 @@ stdenv.mkDerivation rec {
     sha256 = "1wiydkp8a4adwsgfsd688hpv2z7hjv5manhckchk96v6qdsbqk91";
   };
 
+  # Rust refers to jemalloc functions directly so make sure the prefix matchs.
+  configureFlags = [
+    "--with-jemalloc-prefix=je_"
+  ];
+
   meta = with stdenv.lib; {
     homepage = http://www.canonware.com/jemalloc/index.html;
     description = "a general purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support";