Add initial support for the line-height property. Line height is only based on the tallest box in each line and does not factor in the vertical-alignment. Improves whitespace handling by passing the whitespace state between function invocations.
Add link following and refactor the profiler.
Implement scrolling and better zooming
Update rust-layers for GL_LINEAR zooming
Provide an interface to the engine for the script task
handle relative url's when clicking
Refactor flow tree construction and actually use display property.
Implement horizontal scrolling and pinch-to-zoom
Send status messages to the compositor
Spin the event loop every 50 ms to allow Rust channels to be processed.

This is the nail in the coffin for GLUT; we need to fix this.
Resolve relative URLs that begin with '//'
Added a command-line argument for rendering tiles at higher resolutions
Fix URL relativization so that links on Wikipedia work
Add a cheesy progress indicator
Add a spinner for layout
Update submodules
Fix merge fallout
Make script and style display:none
Fix merge fallout which was disabling all CSS classes.
test: Add a box model smoketest