Avoid repeated memchr in SingleSearch
Avoid repeated memchr in SingleSearch

Repeated memchr in BMH slows down the literal search dramatically in
certain corner cases.

SeanRBurton/regex,SeanRBurton/regex,golddranks/regex,rust-lang/regex,rust-lang-nursery/regex,SeanRBurton/regex,edunham/regex,rust-lang/regex,rust-lang/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang/regex,rust-lang/regex,golddranks/regex,rust-lang-nursery/regex,SeanRBurton/regex,edunham/regex,golddranks/regex,edunham/regex,SeanRBurton/regex