2061: big refactor

prepare for next change!
2062: refactor cont..
2065: CssBox.EvaluateComputedValues()

with performance deficit ?!
2066: refactor cont...
2067: refactor
2068: refactor
v2068_1:errs
2069: ok
2072: retro errs
2073 errs!
2075: fix CssLenngth ctor
Merge branch 'v1.7_2069' into v1.7
2076: refactor
Merge branch 'v1.7'