Introduce some extra testing and benchmarking command-line options to

Introduce some extra testing and benchmarking command-line options to
the GTK front end, plus a 'make test' target in the GTK makefile which
uses them to automatically generate 100 puzzles for each game at each
preset configuration, test-run them back through the solver without
their aux_info to ensure that can cope, and produce an HTML box plot
of game generation times for each preset.

As part of this work I've removed the TESTSOLVE mechanism from r9549,
since the new --test-solve option does the same thing better (in that
when something goes wrong it prints the random seed that caused the
problem).

[originally from svn r9825]
[r9549 == 5a095b8a08fa9f087b93c86aea0fa027138b028d]