_Msh_have(): don't use 'command printf' for ksh88 compat
_Msh_have(): don't use 'command printf' for ksh88 compat

bin/modernish:
- I found a bug in ksh88 (Solaris 10.3) where the 'command' builtin
  does spurious parameter expansion on already-expanded arguments
  if the command argument is an external command (with or without
  pathname). For instance,
    a=one b=two
    z='$a and $b'	# literal $a and $b, no expansion
    command printf '%s\n' "$z"
  prints 'one and two', not '$a and $b', on ksh88 (note that
  'printf' is NOT a builtin on that shell).
  Since this only affects external commands with 'command', it is
  too expensive to test for this during init, and it's also not
  really needed as ksh88 as plenty of other fatal bugs. But this
  bug is messing up the error messages of those other fatal bugs on
  ksh88, so remove the use of 'command' from _Msh_have() so it can
  report those fatal error messages gracefully on ksh88.

modernish/modernish