This should decrease the number of allocations before main is entered
significantly, but complicates the code somewhat in return.
Assuming I used `massif` right, doing just `SelfTest --list-tests`
went from 929 allocations at "Remove gcc-4.9 from the travis builds"
(2 commits up), to 614 allocations with this commit.
This allows us to provide machine-readable listings through the
XMLReporter and it will also allow users to define their own listing
format that does whatever their own tools need.
Previously it returned the sum of listed things because ???. This
was completely useless and in many ways actively counterproductive
because of the success/failure conventions around exit codes.
Closes#1410
