Use build-time define to set the path to the source files
directory. Which then can be used to format path to the test
data. This allows running tests from out-of-source-tree -builds
that e.g. QtCreator does.
Test was using and assuming that severity string starts with
capital letter (e.g. "Style"). But the strings are all lowercase
letters.
Ticket #2832 (GUI: XML version 1 test fails)
Kimmo Varis