Revert "fix https://reviews.llvm.org/D22610" and "[compiler-rt] Fix...

Revert "fix https://reviews.llvm.org/D22610" and "[compiler-rt] Fix memmove/memcpy overlap detection on windows"

This currently fails ~500 tests on Darwin:
http://lab.llvm.org:8080/green/job/clang-stage1-configure-RA_check/20456/

This reverts commit 4cfee0dff1facb8fa2827d25c5943bfef96d1a8f and
dbd91205d578cb61ab77be06087e9f65ba8a7ec8.

llvm-svn: 276490