Avoid undefined behaviour when calling memmove(3).
Avoid undefined behaviour when calling memmove(3).

Fixes #154.

Change-Id: Iafc986a11400f47f291fbd225464e2547fdee65e
Reviewed-on: https://code-review.googlesource.com/16370
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

google/re2,google/re2,google/re2,google/re2,google/re2