Avoid memcpy() with same source and destination address.

The behavior of that is undefined, although unlikely to lead to problems in
practice.

Found by running regression tests with Valgrind.

src/backend/tsearch/dict_ispell.c

@@ -127,20 +127,19 @@ dispell_lexize(PG_FUNCTION_ARGS)
 	if (res == NULL)
 		PG_RETURN_POINTER(NULL);
 
-	ptr = cptr = res;
+	cptr = res;
-	while (ptr->lexeme)
+	for (ptr = cptr; ptr->lexeme; ptr++)
 	{
 		if (searchstoplist(&(d->stoplist), ptr->lexeme))
 		{
 			pfree(ptr->lexeme);
 			ptr->lexeme = NULL;
-			ptr++;
 		}
 		else
 		{
+			if (cptr != ptr)
 				memcpy(cptr, ptr, sizeof(TSLexeme));
 			cptr++;
-			ptr++;
 		}
 	}
 	cptr->lexeme = NULL;

src/backend/utils/adt/tsvector.c

@@ -125,6 +125,7 @@ uniqueentry(WordEntryIN *a, int l, char *buf, int *outbuflen)
 				buflen += res->poslen * sizeof(WordEntryPos) + sizeof(uint16);
 			}
 			res++;
+			if (res != ptr)
 				memcpy(res, ptr, sizeof(WordEntryIN));
 		}
 		else if (ptr->entry.haspos)