[ASan] Fix __asan_describe_address and add a test for it.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@213583 91177308-0d34-0410-b5e6-96231b3b80d8
[MSan] Fix strncpy interceptor

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@213590 91177308-0d34-0410-b5e6-96231b3b80d8