Speed up DFA::BuildAllStates() by using the bytemap.
Speed up DFA::BuildAllStates() by using the bytemap.

Change-Id: Id81f67de1b0708817867b65b8e9f0a80e20c5c1c
Reviewed-on: https://code-review.googlesource.com/13970
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

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