engine: fix trigger matching rule

<non-keyword><keyword> is not breakable: $var in php
<keyword><non-keyword> is breakable: func( in c
readme: add defining repetition trigger
add unittest engine
fix xpt#util#UnescapeChar
test:
Merge branch 'f.readme'
Merge branch 'f.test'
Merge branch 'f.engine'
Merge branch 'f.unittest'
Merge branch 'f.util'
remove test and unittest
Merge branch 'f.ex'
dist.140519-5ac0c48