Catch upgrade, preferred form for making modifications

This is mainly about redistributability of the embedded copy of Catch
in the test suite. For example debian policy requires source code to
be distributed in its "preferred form for making modifications".

I took the opportunity to upgrade Catch to version 1.0 build 8, which
required some relatively obvious changes and one patch for Catch,
see https://github.com/philsquared/Catch/pull/195.