Fix generation of too long headline with ShortWords.

Per http://archives.postgresql.org/pgsql-hackers/2008-09/msg01088.php

contrib/tsearch2/wparser_def.c

@@ -298,12 +298,14 @@ prsd_headline(PG_FUNCTION_ARGS)
 				if (curlen < min_words && i >= prs->curwords)
 				{				/* got end of text and our cover is shoter
 								 * than min_words */
-					for (i = p; i >= 0; i--)
+					for (i = p - 1 ; i >= 0; i--)
 					{
 						if (!NONWORDTOKEN(prs->words[i].type))
 							curlen++;
 						if (prs->words[i].item && !prs->words[i].repeated)
 							poslen++;
+						if ( curlen >= max_words )
+							break;
 						if (NOENDTOKEN(prs->words[i].type) || prs->words[i].len <= shortword)
 							continue;
 						if (curlen >= min_words)