Fix two sign comparison mistakes.

Fix two sign comparison mistakes.

Synchronises with:	FreeBSD v1.15 with the notable exception of making
			i an unsigned integer since it need not be negative
			and casting nhosts (a size_t and thus unsigned) to
			it is just the other way around and throws away half
			of the type.  Granted, the chance that you have more
			than 2147483647 hosts (if assuming 32 bit) is a bit
			much, nonetheless, this is the right way to do it in
			my opinion.