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

I have verified that back and forward work once again.
Rename the PrototypeList enums to fix case build warnings.
Have 'mach build' pass arbitrary arguments to Cargo.

Duplicating all of Cargo’s argument parsing in mach is silly.
Remove usage of the deprecated std::num::Zero trait.
Remove usage of deprecated HashMap::get_copy
Simplify util::range::RangeIndex to always require std::num::Int,

and fix remaining warnings.
auto merge of #4420 : servo/servo/fix-warnings, r=Ms2ger
Update layer bounds on resize

This fixes a bug where fixed-position layers are not repositioned when the
window is resized.
auto merge of #4412 : mbrubeck/servo/fixed-layer-resize, r=mrobinson

This fixes a bug where fixed-position layers are not repositioned when the
window is resized.  This can be reproduced with any `position: fixed` element with a `right` or `bottom` position.  I'm not sure how to reftest this, though.

r? @mrobinson
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.