The chown builtin should fail with the same error consistently (#378)

This bug was first reported at <https://www.illumos.org/issues/3782>.
The chown builtin when used on illumos can fail with different error
messages after running the same command twice:

  $ touch /tmp/x
  $ /opt/ast/bin/chown -h 433:434 /tmp/px
  chown: /tmp/x: cannot change owner and group [Not owner]
  $ /opt/ast/bin/chown -h 433:434 /tmp/px
  chown: /tmp/x: cannot change owner and group [Invalid argument]

The error messages differ because the libast struid and strgid
functions will return -2 if the same nonexistent ID is used twice.

The fix for this bug has been ported from here:
4162633a7c

src/lib/libcmd/chgrp.c:
- Remove NOID macro and check for a < 0 error status instead.
  This is different from the Illumos fix at
  <4162633a7c>
  which added another macro.

src/lib/libast/man/{strgid,struid}.3:
- Correct errors in the strgid and struid documentation.
- Document that the strgid and struid functions will return -2 if
  the same invalid name is used twice.

Co-authored-by: Martijn Dekker <martijn@inlv.org>

NEWS

@@ -8,6 +8,11 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 - Fixed a bug introduced on 2020-08-09 that prevented '.' and '..' from
   being completed when using file name tab completion.
 
+- Fixed a bug on illumos that caused the chown builtin to fail with 'Invalid
+  argument' after failing to change the ownership of a file twice using an ID
+  that doesn't exist in /etc/passwd. (Note that the chown builtin is not
+  enabled by default.)
+
 2021-12-11:
 
 - Fixed two more crashing bugs that occurred if ksh received a signal (such