helo.checks: make match_re work

1. precompile the regex list at load time (was: compile every regex on every connection)

2. test regexes, ignore and log error for bad ones

3. load .ini and regex list at register() with config parsing callback (was at connect())

4. added tests for match_re
helo: use valid_regexes from utils
helo: when timed out, provide host name in error
helo: test fix
Merge pull request #584 from msimerson/helo

helo.checks: get match_re working better