Skip debug stepping time in list/func time.

Just makes the debug stats actually useful while stepping.  A bit of
overengineering, but it makes it easy to go frame-by-frame looking for
perf issues.
Enable block transfers in headless for testing.

This allows us to do memory (not just screenshot) tests with GLES, yay.
Merge pull request #6319 from unknownbrackets/debugger

Skip stepping time in debug stats