Load libudev at run-time

Changes the usage of libudev from linking at compile time to loading at
runtime.

Task-number: QTBUG-34176
Change-Id: I7feb91ed3ee1c21dbb3ab508cb7ad6d69c73cc01
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Support HTML5 media context menu items

Support most of the items WebCore populates the context menu with when
the user right clicks an HTML5 audio or video element.

Change-Id: I331a3271f68075fe70d914e2675620f617d53b42
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>