PT42627683 - Small changes in OsTimer implementation to make it safer

Added asserts in OsTimer constructors to verify for NULL parameters. These will log
a CRIT message and will assert.

PT42706949 - Log and assert in case objects receive invalid data
Created a new macro which will print a log message and then it will assert on a condition.
PT42272589 - Proxy wrongfully modifies registrations containing two contacts

Fixed the method which was updating the contacts from a SIP request message with
NAT mappings. This method was updating only the first contact and was using it to
overwrite the remaining contacts. Now it updates each contact.