This patch set results in a working standard library for the asmjs-unknown-emscripten and wasm32-unknown-emscripten targets. It is based on the work of @badboy and @rschulman. It does a few things: Updates LLVM with the emscripten fastcomp patches, which include the pnacl IR legalizer and the asm.js backend. This patch is thought not to have any significant effect on existing targets. Teaches rust