Add tuple-remove-fst, DoWhile-output , DoWhile-output-ith.

[clyben]

tuple-remove-fst take a tuple and return a tuple that the first Non-Tuple(TNil) typed term is removed. DoWhile-output give the output tuple of a loop, which is the body with pred removed. DoWhile-output-ith give the ith-output of a loop.

[clyben]

Actually I think I don't need tuple-remove-fst for now. Shall I close it?

[oflatt]

sure