rt: Remove unnecessary PNaCl specific stubs.
librustc: Add LLVMRustWritePNaClBitcode prototype.
rustllvm: Add wrapper for writing PNaCl bitcode.
Makefiles: Add PNaCl bitcode writing components to the list of components to build.
librustc: Always pass "-pnaclabi-allow-debug-metadata" to LLVM on PNaCl
targets. This is so we can build the std crates with dbg infos and have user
builds without --debuginfo=(1|2) still work.
librustc: Fix Dwarf version mismatch with PNaCl.
librustc: Add The Three required functions for the Ppapi to the list of reachables.