Make JS<T>::clone inline.(fixes #1955)
Annotate 'inline' to TCast::to/to_unchecked/from.
auto merge of #1947 : saneyuki/servo/cast, r=jdm

follow up https://github.com/mozilla/servo/pull/1864#issuecomment-37109672
auto merge of #1966 : lpy/servo/issue1955, r=jdm

see #1955
Refactor assign_height and assign_width for block flow.
Add fixed table test cases
Construct table-related flow and calculate fixed layout
Support a part of anonymous table(step 1-1, 1-2, 2).
Not Covered: step 1-3, 1-4, 3-1, 3-2
*Spec: http://www.w3.org/TR/CSS21/tables.html#anonymous-boxes