Enables case sensitive matching.
Adds possibility to activate and deactivate overlays.

The overlay now stores an additional property 'lambda-lifting which
resolves to an alist. In this alist all necessary information are
stored. The alist is generated during fontification.

An overlay can be disabled (removes 'display, etc.) and enabled
(restores 'display, etc.).

Additionally an buffer-local pre-command-hook is used to disable the
overlays around the point.