vis: use multiple cursor/selection infrastructure

This commits introduces the following keybindings, in normal mode:

 CTRL-N   select word the cursor is currently over, switch to visual mode
 CTRL-P   remove least recently added cursor
 ESC      if a selection is active, clear it.
          Otherwise dispose all but the primary cursor.

In visual mode:

 CTRL-N   create new cursor and select next word matching current selection
 CTRL-X   clear (skip) current selection, but select next matching word
 CTRL-P   remove least recently added cursor

1 files changed, 4 insertions, 1 deletions

diff --git a/view.h b/view.h
index 4e750c0..d0e7070 100644
--- a/view.h
+++ b/view.h
@@ -117,7 +117,10 @@ void view_cursor_to(View*, size_t pos);
 Cursor *view_cursors_new(View*);
 /* get number of active cursors */
 int view_cursors_count(View*);
-/* dispose an existing cursor */
+/* dispose an existing cursor with its associated selection (if any),
+ * not applicaple for the last existing cursor */
+void view_cursors_dispose(Cursor*);
+/* dispose an existing cursor, no matter what */
 void view_cursors_free(Cursor*);
 /* only keep the main cursor, release all others together with their
  * selections (if any) */