[compiler-rt] Fix memmove/memcpy overlap detection on windows

Summary:
The memcpy and memmove functions are the same on windows.
The overlap detection logic is incorrect.

printf-1 test:
```
stdin>:2:114: note: possible intended match here
==877412==ERROR: AddressSanitizer: memcpy-param-overlap: memory ranges [0x0000002bf2a8,0x0000002bf2ad) and [0x0000002bf2a9, 0x0000002bf2ae) overlap
```                                                                                                                 ^

Reviewers: rnk

Subscribers: llvm-commits, wang0109, kubabrecka, chrisha

Differential Revision: https://reviews.llvm.org/D22610

llvm-svn: 276299