Enable multiline input

Adds a nonl() call to avoid translation from \r to \n when pressing
enter.
C-J -> \n
Enter -> \r
To allow multiline input, \n chars (e.g. when pressing C-J) are replaced
with a pilcrow. After hitting enter, every pilcrow is substituted with
\n again.

src/input.c

@@ -42,9 +42,12 @@ void input_new_char(ToxWindow *self, wint_t key, int x, int y, int mx_x, int mx_
 {
     ChatContext *ctx = self->chatwin;
 
+    /* this is the only place we need to do this check */
+    if (key == '\n')
+        key = L'¶';
+
     int cur_len = wcwidth(key);
 
-    /* this is the only place we need to do this check */
     if (cur_len == -1) {
         sound_notify(self, notif_error, 0, NULL);
         return;