id: Add -d and -s options

[des]

Summary

These options may not be combined with any other options and print the
current or specified user's home directory and shell respectively.

[obrien]

usr.bin/id/id.1

53–55

If -d and -s aren't in POSIX p1003.2, please document they are non-standard.

usr.bin/id/id.c

58–59

I'm having trouble finding these function defintions. Are they missing from this diff, or depend on another active review?

[bcr]

OK for the manpage part of the review.

[des]

update

[des]

update man page

[imp]

Other than needlessly libxo-izing this (-P serves 99% of the need there), I think you've done almost all you can to modernize it. Though the (void) casts to fprintf and the like do look a bit archaic. :)

[des]

The motivation here was seeing ports use eval echo ~$user to figure out a user's home directory... “surely there's got to be a better way”