This patch adds 3 new configuration options applicable for
subclasses of ALabel. The options can be used to execute
user defined code in response to the 3 mouse events:
* on-click: The left mouse button click
* on-scroll-up
* on-scroll-down
This patch also modifies the behaviour of the format-alt toggle
such that when the on-click event is configured, format-alt is
toggled on any mouse click other than left click. When on-click
is not defined, any mouse button would toggle format-alt.
Signed-off-by: Harish Krupo <harishkrupo@gmail.com>
