indent(1): Fix off-by-one in control flow leading dead code.

Coverity correctly reported that it's impossible for /comparison/ to be 0
here, because the only way for the for loop to end is by /comparison/
being < 0.

Fortunately the consequences of this bug weren't severe; for duplicated
entries in the typedef names file it would unnecessarily duplicate strings
with strdup(), but pointers to those would replace existing ones. So this
was a memory leak at worst.

CID:	 1361477
Obtained from:	 Piotr Stephaniak

usr.bin/indent/lexi.c

@@ -613,7 +613,7 @@ add_typename(const char *key)
     else {
 	int p;
 
-	for (p = 0; (comparison = strcmp(key, typenames[p])) >= 0; p++)
+	for (p = 0; (comparison = strcmp(key, typenames[p])) > 0; p++)
 	    /* find place for the new key */;
 	if (comparison == 0)	/* remove duplicates */
 	    return;