* constellation: notify embedder when events are hit-tested to browsers
* fix compile error in libsimpleservo
* impl From<&CompositorEvent> for CompositorEventVariant
* remove msg temporaries in Constellation::forward_event
* use single wildcard arm in EventDelivered case in handle_servo_events
This completes the transition to compiling Servo with rust stable. Some
nightly-only features are still used when compiling the `script` and
`crown` crates, as well as for some style unit tests. These will likely
break with newer compiler versions, but `crown` can be disabled for them
conditionally. This is just the first step.
This has some caveats:
1. We need to disable setting up the special linker on Linux. The -Z
option isn't supported with stable rust so using this is out --
meanwhile we can't be sure that lld is installed on most systems.
2. `cargo fmt` still uses some unstable options, so we need to rely on
the unstable toolchain just for running `fmt`. The idea is to fix this
gradually.
This is the start of the organization of types that are in their own
crates in order to break dependency cycles between other crates. The
idea here is that putting these packages into their own directory is the
first step toward cleaning them up. They have grown organically and it
is difficult to explain to new folks where to put new shared types. Many
of these crates contain more than traits or don't contain traits at all.
Notably, `script_traits` isn't touched because it is vendored from
Gecko. Eventually this will move to `third_party`.
