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>

src/lib/libast/man/strgid.3

@@ -38,16 +38,21 @@
 ..
 .TH STRGID 3
 .SH NAME
-strgid \- return group name given group number
+strgid \- return group ID number for given group name
 .SH SYNOPSIS
-.L "char* strgid(int gid)"
+.L "int strgid(const char* name)"
 .SH DESCRIPTION
 .I strgid
-returns the group id name string given the group number
-.IR gid .
+returns the group ID number for the given group name.
 .I strgid
 maintains an internal cache to avoid repeated password database scans
 by the low level
 .IR getgrgid (3).
+On the first error for a given name,
+.I strgid
+returns -1.
+Subsequent errors for the same name will result in
+.I strgid
+returning -2 instead.
 .SH "SEE ALSO"
 getgrent(3)

src/lib/libast/man/struid.3

@@ -38,16 +38,21 @@
 ..
 .TH STRUID 3
 .SH NAME
-struid \- return user name given user number
+struid \- return user ID number for given user name
 .SH SYNOPSIS
-.L "char* struid(int uid)"
+.L "int struid(const char* name)"
 .SH DESCRIPTION
 .I struid
-returns the user id name string given the user number
-.IR uid .
+returns the user ID number for the given user name.
 .I struid
 maintains an internal cache to avoid repeated password database scans
 by the low level
 .IR getpwuid (3).
+On the first error for a given name,
+.I struid
+returns -1.
+Subsequent errors for the same name will result in
+.I struid
+returning -2 instead.
 .SH "SEE ALSO"
 getpwent(3)