"private" symbols which the assember shouldn't strip, but which the linker may remove after evaluation. This is mostly useful for Objective-C metadata. This is plumbing, so we don't have a use of it yet. More to come, etc. llvm-svn: 76385
To-do ----- * Instruction encodings * Tailcalls * Investigate loop alignment * Add builtins * Make better use of lmul / macc