Fix some standards issues and unused variables in theme engine 2.0 WPSC_Cart_Item_Table class.
Cleanup WPSC_Checkout_Wizard
Cleanup WPSC_Controller
Clean up WPSC_Digital_Contents_Table
Clean up WPSC_Message_Collection
Cleanup for WPSC_Product_Variations.  Note: This class seems unfinished.
Cleanup WPSC_Router class.
Cleanup for WPSC_Settings_Form
Clean up WPSC_Settings_Tab_Presentation and _WPSC_Settings_Tab_Form
Cleanup for WPSC_Settings
clean up WPSC_Table
Move the wpsc_is_shipping_enabled function to be globally available.
Remove unused globals and other variables in WPSC_Widget_Category_Drill_Down
Remove currently unused  variable in WPSC_Widget_Product_Categories
Eliminate some dead variables
This needs testing.  Assumptions here, given all the passing by reference, it's a bit hard to follow.  But I don't think  is necessary, and I think  should have been  in form-validation.php:
Seemingly incorrect variable assignment in wpsc_validation_rule_required()
Hopefully use proper variable in _wpsc_filter_rewrite_controller_slugs().  If I'm crazy, this may break stuff.
Hopefully use proper variable in _wpsc_filter_rewrite_controller_slugs().  If I'm crazy, this may break stuff. Previous cmmit was for dead var.
Fix wrong shortcode_atts() call.  Also L207...query_posts()...surely there's a better option.