do not render combining chars on iTerm2.

see: 2eb57cc725

lib/widget.js

@@ -2418,6 +2418,10 @@ Element.prototype.parseContent = function(noTags) {
       // double-width chars will eat the next char after render. create a
       // blank character after it so it doesn't eat the real next char.
       content = content.replace(unicode.chars.all, '$1\x03');
+      // iTerm2 cannot render combining characters properly.
+      if (this.screen.program.isiTerm2) {
+        content = content.replace(unicode.chars.combining, '');
+      }
     } else {
       // no double-width: replace them with question-marks.
       content = content.replace(unicode.chars.all, '??');