Add TEST_SRC_FILES input.
Add TEST_SRC_FILES input.

I've found it convenient to add a TEST_SRC_FILES to list test files that
are interspersed with source, but don't need (or want) coverage output.

jaeguly/cpputest,KisImre/cpputest,cpputest/cpputest,maxilai/cpputest,Andne/cpputest,maxilai/cpputest,PaulBussmann/cpputest,devMichaelJones/cpputest,KisImre/cpputest,offa/cpputest,arstrube/cpputest,devMichaelJones/cpputest,jaeguly/cpputest,dawid-aurobit/cpputest,chenlianbing/cpputest,dawid-aurobit/cpputest,bithium/cpputest,offa/cpputest,Andne/cpputest,cpputest/cpputest,Mindtribe/cpputest,maxilai/cpputest,offa/cpputest,PaulBussmann/cpputest,PaulBussmann/cpputest,basvodde/cpputest,Andne/cpputest,arstrube/cpputest,offa/cpputest,arstrube/cpputest,PaulBussmann/cpputest,cpputest/cpputest,chenlianbing/cpputest,Mindtribe/cpputest,asgeroverby/cpputest,basvodde/cpputest,asgeroverby/cpputest,bithium/cpputest,chenlianbing/cpputest,Andne/cpputest,dawid-aurobit/cpputest,jaeguly/cpputest,jaeguly/cpputest,devMichaelJones/cpputest,dawid-aurobit/cpputest,asgeroverby/cpputest,KisImre/cpputest,chenlianbing/cpputest,KisImre/cpputest,devMichaelJones/cpputest,maxilai/cpputest,Mindtribe/cpputest,basvodde/cpputest,bithium/cpputest,cpputest/cpputest,bithium/cpputest,asgeroverby/cpputest,basvodde/cpputest,Mindtribe/cpputest,arstrube/cpputest