Expand the comment on the \p and \P limit.
Expand the comment on the \p and \P limit.

Change-Id: Ib2f359f8ecc4172754a2b02458fc64698e8c1daf
Reviewed-on: https://code-review.googlesource.com/18990
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

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