Reduce recalc/layout during the compositing of animated values.

Previously we would cause a recalc and layout for each animated
target/property pair, for every frame. With this change only one recalc/layout
is required per frame.
Reformat test-calc-checks
Rebaseline test-calc-checks
Merge pull request #354 from dstockwell/reduce-recalc-layout

Reduce recalc/layout during the compositing of animated values.
First pass at new type, blocked on clean up change pending
Save point
Updated position list parser and wrote tests
Fix zero() reference bug
Added missing impl unit tests
Added disabled layout test
Removed webkit prefix
Put prefix support for calc back
Put auto support back into percentLengthType RE
Fix typo in comment
Nits
Review changes
Updated layout test
Minor changes to test case