more SCTP parser fixes
only create sctpmaps when needed
Merge pull request #116 from nils-ohlmeier/multistream

More SCTP improvements
Merge pull request #117 from docfaraday/multistream_unit_tests

Add some testing for fallback, some testing that media-level-only
Fix a pedantic compiler error.
Fix another pedantic compiler error, and make a test-case fixtureless
since it didn't use the fixture.