Fix bug in bounds of select node.
Added ability to run any or all tests under valgrind.
Continuing to mess with bounds inference to fix autotuning bugs

We're not there yet, but this checkpoint is only a little bit broken
and only a little bit slow, and I believe it's better than what's currently
checked in.

HL_TARGET=ptx interpolate is slow because storage inference operates
inside-out and considers both calls and provides.

Some schedules may cause uncaught out-of-bounds reads on inputs, because
the current bounds inference logic does something awkwardly in between
checking what will be loaded and checking what is necessary for a correct
output.