check validity for to/from in sipmsg_validate
sanity check for contact header(s)
indentation with tabs, correct typos, remove escaped quotes. thank you Walter Doekes for the code review.
Merge pull request #294 from tallicamike/feature-sipmsgvalidate-for-tofrom

sipmsgops: Additional "f", "t" and "c" flags for sipmsg_validate() which check To, From and Contact header integrity