[LLVM-C] Add LLVM{IsConstantString,GetAsString,GetElementAsConstant}.
[OCaml] Add Llvm.{string_of_const,const_element}.
PR11778: Fix the rejects-valid half of this bug. We still produce the same
poorly-worded warning for a case value that is not a possible value of the
switched-on expression.
[x86] Fix the test case added in r214670 and tweaked in r214674 further.

Fundamentally, there isn't a really portable way to test the constant
pool contents. Instead, pin this test to the bare-metal triple. This
also makes it a 64-bit triple which allows us to only match a single
constant pool rather than two. It can also just hard code the '.' prefix
as the format should be stable now that it has a fixed triple. Finally,
I've switched it to use CHECK-NEXT to be more precise in the instruction
sequence expected and to use variables rather than hard coding decisions
by the register allocator.
[x86] Handle single input shuffles in the SSSE3 case more intelligently.

I spent some time looking into a better or more principled way to handle
this. For example, by detecting arbitrary "unneeded" ORs... But really,
there wasn't any point. We just shouldn't build blatantly wrong code so
late in the pipeline rather than adding more stages and logic later on
to fix it. Avoiding this is just too simple.
MemoryBuffer: Don't use mmap when FileSize is multiple of 4k on Cygwin.

On Cygwin, getpagesize() returns 64k(AllocationGranularity).

In r214580, the size of X86GenInstrInfo.inc became 1499136.

FIXME: We should reorganize again getPageSize() on Win32.
MapFile allocates address along AllocationGranularity but view is mapped by physical page.