Adjust fold-widget visibility based on folding-enabled

Slight adjustment to the visibility of `.ace_fold-widget` so that when the `.ace_folding-enabled` flag is toggled, so is the widget's visibility. This addresses the issue where the left-most edge of the folding widgets may still be visible after disabling code. folding
Addresses an issue where IE8 does not properly handle the RegExp in _parseTag, causing folding not to work for the XML mode (or modes that inherit XML). Tested XML mode in IE8/9 and major browsers. Should resolve ajaxorg/ace#1384
Merge pull request #1394 from rgriffith/ie8_xml_folding_fix

Addresses an issue where IE8 does not properly handle the RegExp in _par...
Merge pull request #1387 from rgriffith/folder-widget-css-improvement

Adjust fold-widget visibility based on folding-enabled
Fix for replaceAll in a range. Fix for no session ace
Merge pull request #1395 from ajaxorg/fix/searchAll

Fix for replaceAll in a range. Fix for no session ace