Merge pull request prototypejs#108 from jwestbrook/issue-3701-fix

Be more liberal in what we accept as an opacity value in old IE.

Author: savetheclocktower

src/prototype/dom/dom.js

@@ -3062,7 +3062,7 @@
 
     var filter = Element.getStyle(element, 'filter');
     if (filter.length === 0) return 1.0;
-    var match = (filter || '').match(/alpha\(opacity=(.*)\)/);
+    var match = (filter || '').match(/alpha\(opacity=(.*)\)/i);
     if (match && match[1]) return parseFloat(match[1]) / 100;
     return 1.0;
   }