Add support for small-caps font-variant.

Ref: 2554.
Disable non_snake_case warnings in devtools
Fix other warnings in devtools
Avoid an unnecessary string allocation in allow_cross_origin_request.
Add #[jstraceable] syntax extension
Add fixme comment for future work, make scale factor a constant.
Merge pull request #3461 from mbrubeck/warnings

Fix misc warnings in devtools crates. r=jdm
Handle null strings in Namespace::new.

This also avoids a string copy in the rare case of an unrecognized namespace.
Merge pull request #3462 from Ms2ger/as-slice

Avoid an unnecessary string allocation in allow_cross_origin_request; r=jdm
Remove redundant into_string() calls.
Allow resolution to be configured on command line. Default to 1280x1024.
Change default back to 800x600 as mac travis builders don't work with 1280x1024
Add untraceable! macro
Change opts to work in screen pixels that are scaled to device pixels.
layout: Implement `white-space: nowrap`.

Improves the Reddit header.
Merge pull request #3459 from glennw/small-caps

Add support for small-caps font-variant.
Use JSTraceable everywhere
Update docs
Merge pull request #3466 from Ms2ger/into_string

Remove redundant into_string() calls.; r=jdm
Merge pull request #3458 from pcwalton/whitespace-nowrap

layout: Implement `white-space: nowrap`.