KMP_USE_FUTEX preprocessor definition defined in kmp_lock.h is used
inconsequently throughout LLVM libomp code.

* some .c files that use this define do not include kmp_lock.h file,
  in effect guarded part of code are never compiled
* some places in code use architecture-depending preprocessor
  logic expressions which effectively disable use of Futex for
  AArch64 architecture, all these places should use
  '#if KMP_USE_FUTEX' instead to avoid any further confusions
* some places use KMP_HAS_FUTEX which is nowhere defined,
  KMP_USE_FUTEX should be used instead

Differential Revision: http://reviews.llvm.org/D19629

llvm-svn: 269642