Updates YUICompressor to version 2.4.8

YUI Compressor 2.4.8
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+ Fix "important" and conditional comment processing
+ Fix a bug in the support for JS 1.7 style getters/setters
+ Better compliance and results in CSS compression (@danbeam,
  @faisalman, @killsaw, @ademey)
+ Now minifies "border-left" in CSS (@sbertrang)
+ Include filename in warning and error output (@danielbeardsley)
+ Many improvements to parameter parsing and batch modes (@bmouw,
  @bandesz, @ryansully)
+ Include jQuery as part of our test suite (@apm)
+ Trim trailing commas where possible (@nlalevee)