I've been fixing parts of the tree that do uid and gid parsing so that
incorrect values don't default to `0' (see discussion on tech-security)
for more info.

To do this, I've been converting the use of atoi() to strtoul(), and
checking appropriate values to ensure that the parsed field was just a
number.

However, on the alpha, the return value of strtoul() is a unsigned 64
bit long, which may exceed the size of uid_t (unsigned 32 bit int).

So, I would like to create the following defines in <limits.h> or
<machine/limits.h>, and check against them in the relevant areas:
	#define		UID_MAX		4294967294	/* 2^32 - 2 */
	#define		GID_MAX		4294967294

It's 2^32-2 because setreuid treats -1 as a special value.

I had thought about using 2147483647 (2^31-1), because of setreuid()
That halves the size of the uid space, however.

Comments?