Simplify a really complicated check for Arch == X86_64.

The function hasReliableSymbolDifference had exactly one use in the MachO
writer. It is also only true for X86_64. In fact, the comments refers to
"Darwin x86_64" and everything else, so this makes the code match the
comment.

If this is to be abstracted again, it should be a property of
TargetObjectWriter, like useAggressiveSymbolFolding.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203605 91177308-0d34-0410-b5e6-96231b3b80d8
[mips] Implement NaCl sandboxing of function calls:

  * Add masking instructions before indirect calls (in MC layer).
  * Align call + branch delay to the bundle end (in MC layer).

Differential Revision: http://llvm-reviews.chandlerc.com/D3032


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203606 91177308-0d34-0410-b5e6-96231b3b80d8
support: add a utility function to normalise path separators

Add a utility function to convert the Windows path separator to Unix style path
separators.  This is used by a subsequent change in clang to enable the use of
Windows SDK headers on Linux.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203611 91177308-0d34-0410-b5e6-96231b3b80d8