fix text-decoration property in layout & fix line-height property

[ksh8281]

add inline stuff & color support
it makes same result with firefox in "http://www.w3.org/Style/CSS/Test/CSS1/current/sec543.htm"
makes line-height property can inherit

[highfive]

Warning

• These commits modify layout code, but no reftests are modified. Please consider adding a reftest!
• @ksh8281, please confirm that src/test/html/acid1.html and your favourite wikipedia page still render correctly!

[ksh8281]

r? @pcwalton

[pcwalton]

This makes sense, but it seems rare that underline/overline/text-decoration could be a different color from the color. Maybe we should not store separate colors in every flow, but rather have something like Option<~RareFlowFlags> with:

struct RareFlowFlags {
    underline_color: Color,
    overline_color: Color,
    line_through_color: Color,
}

If rare_flow_flags is None, then it would be assumed that the underline/overline/line through colors are the same as the text color. This would save memory in the common case.

[ksh8281]

@pcwalton i think there is no way to compare color when propagate data.
because there is not information about color or style.
so i apply your opinion in other way.
r?