Fix typing of srandom() and initstate().

POSIX requires that these functions have an unsigned int for their first
argument; not an unsigned long.

My reasoning is that we can safely change these functions without
breaking the ABI. As far as I know, our supported architectures either
use registers for passing function arguments that are at least as big as
long (e.g., amd64), or int and long are of the same size (e.g., i386).

Reviewed by: ache
Differential Revision: https://reviews.freebsd.org/D6644