Revert "Add support for attribute 'noescape'."

This reverts commit r313722.

It looks like compiler-rt/lib/tsan/rtl/tsan_libdispatch_mac.cc cannot be
compiled because some of the functions declared in the file do not match
the ones in the SDK headers (which are annotated with 'noescape').

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@313725 91177308-0d34-0410-b5e6-96231b3b80d8