[ASan] Add the memcmp_strict flag (1 by default) that controls the behavior of accessibility checks in memcmp.
1: memcmp(p1, p2, n) always checks n bytes
0: memcmp checks up to n bytes depending on whether the memory contents differ.



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@176256 91177308-0d34-0410-b5e6-96231b3b80d8