Split block level file hashing out of main() to it's own file.

	Rename block_hash.c to main.c since its namesake is no longer
	contained within itself.

	Move most libgcrypt stuff to hashops.c since it's the only place
	it's used.

	Same for print_hash().

	Update Makefile accordingly.
Add -Wall to Makefile. Fix a couple of warnings.
Move hash comparison out of main.