Move common macros into a new crate (fixes #1882)
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
Remove some unnecessary transmutes.

These can either be done by implicit `&` -> `*` coercions, explicit `*`
-> `*` casts, or an explicit `&*x` `*` -> `&` re-borrow (which is still
unsafe, but significantly more controlled compared to a `transmute`).
Set a name for WorkQueue tasks (fixes #1830)
auto merge of #1958 : mbrubeck/servo/macro-crate, r=kmcallister

This moves the bitfield! macro into a new shared `macros` crate as suggested in #1882.
auto merge of #1973 : june0cho/servo/table_rebase, r=larsbergstrom,metajack

This is a rebase of #1548 on recent master.

There have been many changes since #1548 is first uploaded, so I'm creating new PR.
This PR includes:
 - construction of table-* flows (table-wrapper, table-caption, table, table-rowgroup, table-row, table-cell)
 - fixed-layout table calculation
 - a part of anonymous table object implementation 
[CSS 2.1, 17.2.1](http://www.w3.org/TR/CSS21/tables.html#anonymous-boxes) (Step 1-1, 1-2, Step 2)
auto merge of #1977 : mbrubeck/servo/task-name, r=jdm

Now with 100% less breaking everything.  (An earlier version of this patch in #1948 switched WorkQueue from native tasks to green tasks, which I missed in testing because we don't spawn new layout threads by default on 1- or 2-core machines.)
auto merge of #1978 : huonw/servo/less-transmute, r=Ms2ger

These can either be done by implicit `&` -> `*` coercions, explicit `*`
-> `*` casts, or an explicit `&*x` `*` -> `&` re-borrow (which is still
unsafe, but significantly more controlled compared to a `transmute`).
Added CollectionFilter, CollectionTypeId
Implemented HTMLCollection::create_live
Support live HTMLCollection for Document collections

The following interface methods now return live collections:
Document.{images,embeds,plugins,links,forms,scripts,anchors,applets}
Support live HTMLCollection for FieldSet.elements
Support live HTMLCollection for DataListElement.options
Updated HTMLCollection content test
HTMLCollection::create returns live collections by default
Implemented Document.importNode

Spec:
http://dom.spec.whatwg.org/#dom-document-importnode
Implemented Node.adoptNode

Spec:
http://dom.spec.whatwg.org/#dom-document-adoptnode