Handle NSAttributedString inputs (bug#29837)

; Do not merge to master.

* src/nsterm.m (EmacsView::insertText): Handle NSAttributedString.

src/nsterm.m

@@ -6317,11 +6317,18 @@ flag set (this is probably a bug in the OS).
          by doCommandBySelector: deleteBackward: */
 - (void)insertText: (id)aString
 {
-  NSString *s = aString;
-  NSUInteger len = [s length];
+  NSString *s;
+  NSUInteger len;
 
   NSTRACE ("[EmacsView insertText:]");
 
+  if ([aString isKindOfClass:[NSAttributedString class]])
+    s = [aString string];
+  else
+    s = aString;
+
+  len = [s length];
+
   if (NS_KEYLOG)
     NSLog (@"insertText '%@'\tlen = %lu", aString, (unsigned long) len);
   processingCompose = NO;