textiter: fix bug in FindLogAttrFunc functions

attrs[len] is the last PangoLogAttr available, at the iter position after the
last character of the line.

For a line in the middle or the start of the buffer, the '\n' is taken
into account by 'len'. For example the is_word_end is generally reached
before the '\n', not after. But for the last line in the buffer, where
there is no trailing '\n', it is important to test until attrs[len].

The bug didn't occur before because find_by_log_attrs() worked directly
on the iter passed as the function argument. But now it is no longer the
case.

https://bugzilla.gnome.org/show_bug.cgi?id=618852

gtk/gtktextiter.c

@@ -2895,7 +2895,7 @@ find_word_end_func (const PangoLogAttr *attrs,
     ++offset;
 
   /* Find end of next word */
-  while (offset < len)
+  while (offset <= len)
     {
       if (attrs[offset].is_word_end)
         {
@@ -2982,7 +2982,7 @@ find_sentence_end_func (const PangoLogAttr *attrs,
     ++offset;
 
   /* Find end of next sentence */
-  while (offset < len)
+  while (offset <= len)
     {
       if (attrs[offset].is_sentence_end)
         {
@@ -3580,7 +3580,7 @@ find_forward_cursor_pos_func (const PangoLogAttr *attrs,
   if (!already_moved_initially)
     ++offset;
 
-  while (offset < len)
+  while (offset <= len)
     {
       if (attrs[offset].is_cursor_position)
         {