Upgrade to ExtJS 3.4.0 (IE9 Specific bugfixes)

Here is the Release Notes for this version:

Release Notes for Ext JS 3.4.0

Release Date: June 9, 2011
Current Version: 3.4.0 (rev 7395/288)
Previous Version: 3.3.3 (rev 7389/286)
Changes

Menu

Incorrect menu width on IE9
Fix Reorderable example
Form/Field

Fix an issue with composite fields being marked incorrectly
Trigger fields are now flushed with fields on IE9
Fix field width in IE9
Fix fieldset header checkboxes in IE9 quirks
Misc

Allow altText to be specified on a per item basis for grid columns
Ensure there's no bottom margin on the multi-select
Apply additional css classes for IE9 (ext-ie9 and x-quirks)
Apply additional boolean flags for IE9 (Ext.isIE9 and Ext.isIEQuirks)
Add support to insertHTML method to prevent createContextualFragment errors with IE9