Fix the DFA memory budget logic for RE2::Set.
Fix the DFA memory budget logic for RE2::Set.

Change-Id: I10dafc05ba500e218cbb5dfe65c9297944eb7135
Reviewed-on: https://code-review.googlesource.com/5160
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

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