improve processing stylesheet properties

improve processing stylesheet properties

By scanning the properties in reverse order we don't have to save
properties in the list only to remove them later when the occur
again. It's also unnecessary to cache the values since they can
be easily plucked out of decls. Various other tests can be done
once per property instead of once per property occurence in decls.

Change-Id: I81cf60c59efaeed57fc9c12df98279d6cae116cd
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Rick Stockton <rickstockton@reno-computerhelp.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>
Reviewed-by: John Brooks <john.brooks@dereferenced.net>