The memchr implementation for 64 bit fails if these conditions occur:
- The buffer is 32 byte aligned.
- The buffer contains the character in the first byte.
- The count sent in is zero.
The function should return NULL, but it's not.
Bug: 16676625
Change-Id: Iab33cc7a8b79920350c72f054dff0e0a3cde69ce