Small changes to test and CI infrastructure

Travis is now configured such that ctest will be invoked with the
--output-on-failure option, which will dump the test output from the
failing test.

The cmake configuration is also configured to call the test program with
the -v option, which causes it to include the test names in the output as
they run.

The end result should make it much easier to debug problems that occur
during CI builds.
Minor changes to debug logging behavior in mrp.c and msrp.c

* Hide logging of unrecognized attribute types behind LOG_MSRP guard.

* Make msrp_attrib_type_string non-static so it can be called from tests.

* Add MRP_CPPUTEST to the list of conditions that enables debug printing
   functions in mrp.c
Move test double code for mrpd into its own file and some enhancements.

This moves test double code from AllTests.cpp into newly-created
mrp_doubles.c|h and updates the existing test code and, to a small degree,
code under test, to accomodate the change.

State was added to mrp_doubles to track call parameters to mrpd functions
and to provide some other debug/test functionality.

Enhancements include instrumentation of the msrp_event function, which
will provide the basis for testing of MSRP's MRPDU parsing function.
A set of unit tests for MSRP MRPDU parsing.

This tests a variety of scenarios related to both well-formed and malformed
MSRP packets. Tests of all common scenarios pass, but some odd corner cases
were found that should be looked at.

The tests that fail are defined with IGNORE_TEST so that the CI build
won't fail.