[PATCH] AArch64: Add command line option to select big or little endian

[Simon Atanasyan]

  Support -EB/-EL is essential for MIPS. But I do not see any problems in inverting the aliasing. It looks like we need to change only a couple of lines in the `computeTargetTriple()` routine in that case.

http://llvm-reviews.chandlerc.com/D3215