This patch improves performance for input string which doesn't match
even the first part of a pattern.  Although there is no less effective
for grep as it uses a superset of DFA, gawk speeds up about 40%.

$ time -p env LC_ALL=ja_JP.eucJP ./gawk '/k/ { print }' ../k

(before)
  real 2.85  user 2.79  sys 0.05

(after)
  real 1.70  user 1.64  sys 0.06

I think that this improvement should have been performed in bug#17576.