Add many prototypes and ANSI-ize 'patch. Not a complete job of it, but it gets

Add many prototypes and ANSI-ize 'patch.  Not a complete job of it, but it gets
our patch to look a little more like NetBSD's, and has the nice characteristic
that the object code is exactly the same after the change as before it (even in
patch.c and pch.c, which have pesky 'assert' statements in them).

Reviewed by:	/sbin/md5 on i386, alpha, sparc64
MFC after:	3 days