hash-process! and hash-done! should take optional arguments start and end

[Takashi Kato]

It's better to enhance these procedures to prevent unnecessary memory allocation.

To avoid breaking backward compatibility, C side of the procedures should check arity.

[Takashi Kato]

Adding start/end argumet to hash-process! and hash-done! (Fixes #99)

→ <<cset 7ee1ddb455b1>>