[matchbrackets addon] Work around IE7 bug

Where it mysteriously makes the editor stop working (typed input no longer goes to
textarea) whenever highlighting fires.

Issue #1193

addon/edit/matchbrackets.js

 (function() {
+  var ie_lt8 = /MSIE \d/.test(navigator.userAgent) &&
+    (document.documentMode == null || document.documentMode < 8);
+
   var matching = {"(": ")>", ")": "(<", "[": "]>", "]": "[<", "{": "}>", "}": "{<"};
   function findMatchingBracket(cm) {
     var cur = cm.getCursor(), line = cm.getLineHandle(cur.line), pos = cur.ch - 1;
@@ -38,6 +41,9 @@
                           {className: style});
     var two = found.to && cm.markText(found.to, {line: found.to.line, ch: found.to.ch + 1},
                                       {className: style});
+    // Kludge to work around the IE bug from issue #1193, where text
+    // input stops going to the textare whever this fires.
+    if (ie_lt8 && cm.state.focused) cm.display.input.focus();
     var clear = function() {
       cm.operation(function() { one.clear(); two && two.clear(); });
     };