The planned support for true A over IP requires the encoding and
decoding of a so called "AoIP Transport Layer Address" element.
This commt adds parsing functionality and tests for the element
mentioned above, however, it is not yet actively used.
Change-Id: I57933b0a06a3f54ec2a41e6ecb6ced9fbbc89332
This tests verifies the content of the GSM 08.08 messages, it does
not verify the remaining headroom (which the SCCP/IPA code relies
on being plenty to prepend the header). More to come in the future.