Use most recent sms db, if multiple are found.
Add build_msg_query_ios6().

iOS 6 introduced a new schema, necessitating a new query.
Convert date and address for iOS 6.

* Add functions: convert_date_ios6() and convert_address_ios6().
* Test for ios_db_version in main() to call correct functions for
  ios5 and ios6 DB schemas.
Add which_db_version().

* Queries for new `handle` table, which was introduced with
  iOS 6.
Continue to truncate phone numbers to 10 digits.

* Use the 10-digit phone number in queries to find matching
  texts in DB. Otherwise, users will have to specify '+1' at
  the beginning of phone numbers on command line, which would be
  an unnecessary UI change...and just plain annoying.
Move looping through DB rows into new functions.

* Add get_messages() and get_messages_ios6().