script: Fix double borrow error when going back. Closes #4402.

I have verified that back and forward work once again.
net: Remove glob imports added in #4405
gfx: Remove glob imports added in #4405
This fixes #4407. This removes all unnecessary clones when calling fire_timer.
auto merge of #4416 : mattnenterprise/servo/fire-timer-clone, r=jdm

I tested that it worked correctly by using running './mach run tests/html/test_timeout.html' and making sure the timers went off.
style: Remove glob imports added in #4405
Fix some writing mode mismatch assertions errors.

The rendering is still wrong beause of #2795, but at least we get a rendering.

(This test change is just for readability, it should be equivalent to before.)
Add the basic CSSStyleDeclaration CSSOM interface.

This just includes the .webidl file (with some of the functionality
commented out) and the stub implementations for the bindings.

This is another step towards #1721.
Add stub CSS2Properties type.
Stub in some uses of getPropertyValue and sketch out its implementation.
Add a style property to HTMLElement.
Implement something like CSS value serialization. Fetch actual inline style declarations from owning elements.
Implement setting element style properties. Improve serialization to return initial values when unspecified.
Improve color serialization by retaining author-specified keywords.
Add a ton of properties and improve a bunch of serialization.
Fixups for rust upgrade and jsref changes.
Rebase and update new css properties.
Add z-index support.
Move test_htmlelement_style.html out of the automatic tests because they don't all pass.
Implement RemoveProperty, SetProperty, and supported property indices.