res_pjsip: Add TLSv1.1 and TLSv1.2 support

Support for these protocols was added in the same commit as the 'proto'
field, so we can safely use the same ./configure check.

For reference: https://trac.pjsip.org/repos/changeset/4968

Change-Id: Icf4975d785d6bfb8f30ac7ffa695a0adf9382dac