sh: Remove XXX comment about removing nextopt().

Using nextopt() avoids depending on the BSD-specific optreset feature in
getopt() and reduces code size (both source and binary).

bin/sh/options.c

@@ -531,10 +531,6 @@ out:
 }
 
 /*
- * XXX - should get rid of.  have all builtins use getopt(3).  the
- * library getopt must have the BSD extension static variable "optreset"
- * otherwise it can't be used within the shell safely.
- *
  * Standard option processing (a la getopt) for builtin routines.  The
  * only argument that is passed to nextopt is the option string; the
  * other arguments are unnecessary.  It return the character, or '\0' on