whitespace
Fix a crash that occurs when PWD is invalid.

MCJIT needs to be able to run in hostile environments, even when PWD
is invalid. There's no need to crash MCJIT in this case.

The obvious fix is to simply leave MCContext's CompilationDir empty
when PWD can't be determined. This way, MCJIT clients,
and other clients that link with LLVM don’t need a valid working directory.

If we do want to guarantee valid CompilationDir, that should be done
only for clients of getCompilationDir(). This is as simple as checking
for an empty string.

The only current use of getCompilationDir is EmitGenDwarfInfo, which
won’t conceivably run with an invalid working dir. However, in the
purely hypothetically and untestable case that this happens, the
AT_comp_dir will be omitted from the compilation_unit DIE.
Revert a final patch that was committed without the author contributing
it to the LLVM project through the appropriate channels.

This reverts:
r195837: "[Sanitizer] Add rudimentary support for using libbacktrace in ..."
Fix miscompile of MS inline assembly with stack realignment

For stack frames requiring realignment, three pointers may be needed:
- ebp to address incoming arguments
- esi (could be any callee-saved register) to address locals
- esp to address outgoing arguments

We would use esi unconditionally without verifying that it did not
conflict with inline assembly.

This change doesn't do the verification, it simply emits a fatal error
on functions that use stack realignment, dynamic SP adjustments, and
inline assembly.

Because stack realignment is common on Windows, we also no longer assume
that MS inline assembly clobbers esp.  Instead, we analyze the inline
instructions for implicit definitions and check if esp is there.  If so,
we require the use of a base pointer and consider it in the condition
above.

Mostly fixes PR16830, but we could try harder to find a non-conflicting
base pointer.

Reviewers: sunfish

Differential Revision: http://llvm-reviews.chandlerc.com/D1317
Make anonymous namespace as small as possible.

Use of static is recommended by the style guide.
Revert "Fix miscompile of MS inline assembly with stack realignment"

This reverts commit r196876.  Its tests failed on the bots, so I'll
figure it out tomorrow.
Whitespaces.
Add proper dependencies to LLVMBuild.txt in llvm/lib.

I'll prune redundant deps in LLVMBuild.txt, later.
GCOV.cpp: Use PRIu64 instead of %lu.
Style fixes. No functionality change.
Skip the body of a loop as early as possible.
[AArch64 NEON] Support poly128_t and implement relevant intrinsic.
[AArch64 NEON] Support poly128_t and implement relevant intrinsic.
[AArch64 NEON] Replace fpimm with fpz32 for floating compare with zero.
  This is a small change to be strict. Just want get pattern safer.
Remove data members used for relocations

... because they are used only in the function for relocations.
Add more const qualifiers.