find: If a part of an expression is unknown, do not call it an option.

Although most of the primaries and operators start with "-", they are not
options.

Examples:
  find . -xyz
  find . -name xyz -or bad

MFC after:	1 week

usr.bin/find/option.c

@@ -172,7 +172,7 @@ find_create(char ***argvp)
 	argv = *argvp;
 
 	if ((p = lookup_option(*argv)) == NULL)
-		errx(1, "%s: unknown option", *argv);
+		errx(1, "%s: unknown primary or operator", *argv);
 	++argv;
 
 	new = (p->create)(p, &argv);