text: remove text_history_get function

As currently implemented this does not properly integrate with
multiple cursor support. The functionality should be provided
in a layer higher up.

The jumplist and changelist need to be redesigned, for now they
are broken.

text.c

@@ -1675,15 +1675,3 @@ size_t text_mark_get(Text *txt, Mark mark) {
 
 	return EPOS;
 }
-
-size_t text_history_get(Text *txt, size_t index) {
-	for (Revision *rev = txt->current_revision ? txt->current_revision : txt->history; rev; rev = rev->prev) {
-		if (index-- == 0) {
-			Change *c = rev->change;
-			while (c && c->next)
-				c = c->next;
-			return c ? c->pos : EPOS;
-		}
-	}
-	return EPOS;
-}

text.h

@@ -357,7 +357,4 @@ ssize_t text_write_range(Text*, Filerange*, int fd);
 bool text_mmaped(Text*, const char *ptr);
 /** @} */
 
-/* get position of change denoted by index, where 0 indicates the most recent */
-size_t text_history_get(Text*, size_t index);
-
 #endif

vis-motions.c

@@ -187,7 +187,7 @@ static size_t window_changelist_next(Vis *vis, Win *win, size_t pos) {
 		cl->index = 0;
 	else if (cl->index > 0 && pos == cl->pos)
 		cl->index--;
-	size_t newpos = text_history_get(txt, cl->index);
+	size_t newpos = pos;
 	if (newpos == EPOS)
 		cl->index++;
 	else
@@ -204,7 +204,7 @@ static size_t window_changelist_prev(Vis *vis, Win *win, size_t pos) {
 		cl->index = 0;
 	else if (pos == cl->pos)
 		win->changelist.index++;
-	size_t newpos = text_history_get(txt, cl->index);
+	size_t newpos = pos;
 	if (newpos == EPOS)
 		cl->index--;
 	else