BF: fix regex for openssh-6.3
DOC: ChangeLog for filter.d/sshd
BF: filter.d/sshd group on md5hex and () for serial needed to be escaped
DOC/ENH: __md5hex regex defination to common.conf. Document debian bug #
Merge pull request #371 from grooverdan/ssh-6.3

BF: fix regex for openssh-6.3