update legend title
Add function prefix description
do not check benchmark program
Add OP_EXPECT_MORE_ALPHA opcode
when matching pcre do not switch check rc
document about optimization and slug
update doc
partially
Update changelog
Update README.md
Fix the extra "check" checking
Add --enable-check option
do not install benchmark to prefix/bin
remove AM_PATH_CHECK
check check.h automatically
unset if config.h is not found.
TESTS += benchmark
fix configure script for check
update .travis.yml config
update README for steps