Fix for issue #16527: incorrectly combining literals that shouldn't be combined -- (LIT1 - expr)+LIT2, when LIT2 is a string.
Fix bug where output failed when CSS class names started with a numeric digit (I know, but some browsers actually allow that)
Allow for conditional-compilation comments that only contain a ! within expressions.
Add ability to ignore specific CSS errors via the -ignore switch.
Add ability to specify ignore-errors via the build task (both JS and CSS)