Link now caches imports. That means importing the same library (say, Qt)
from more than one file no longer creates an importing namespace for
each one. Instead, a single one is created for the instance of Link.
To make this work, the type environment in ScopeChain has been given its
own type: Interpreter::TypeEnvironment. That has the added benefit of
being able to carry meta-information about imports. You can use
TypeEnvironment::importInfo(qmlComponentName) to get information about
the import node that caused the import of the component.
* If possible, create LookupContexts through SemanticInfo; it caches the
linked Context and will be faster.
* Contexts now own their Engine.
Reviewed-by: Lasse Holmstedt
Instead of only maintaining a flat list of scopes, actually store the
global, component chain, root object, scope object, function, id and js
scopes separately.
* Add SemanticHighlighter to QmlJSTextEditor to update the semantic info
in a background thread.
* Add QmlJS::Check to run semantic checks on qml and js documents.
* Add a check for incorrect property names.
* Fix hoverhandler to show tool tips from extra selections over help
tooltips.
