[PATCH] MachO: support N_INDR aliases in the assembler

[kledzik at apple.com]

What is the visibility of alias symbols?  An earlier patch had them global by default, which is unlike other symbols in assembler which are non-extern by default.  

The test case relies on the order of the symbols (or relies on llvm-nm sorting them a certain way). Is there a defined order to where the N_INDR symbols are in the symbol table? The range of global symbols are sorted alphabetically.  

Since no public linker supports this yet, we need to make sure that the C side is not enabled and hope no assembly files rely on the old behavior.

http://reviews.llvm.org/D3892