#95 h-like while loop

[Martin Büttner]

A loop like h which doesn't pop anything from the stack can easily be defined as a while loop, by checking the top of the stack before entering the loop. I'm not suggesting to replace h, but just add an additional two-character loop. This would allow for a while-loop without needing a second block.

If both this and https://sourceforge.net/p/cjam/tickets/87/ are implemented, this new loop should ultimately pop the condition as well.