[asan] Avoid hooking memchr() on Windows64

There is not enough padding in front of memchr(), and, the first 6 bytes
contains a branch instruction. Basically the current interception will
not work on memchr().

It was disabled before, but was missing the part to disable it for
INTERCEPT_LIBRARY_FUNCTION.

Patch by Wei Wang

Differential Revision: https://reviews.llvm.org/D22371

llvm-svn: 275494