and ClickLightHdl always takes a non-NULL argument, so NULL test is
pointless. Turn it into a normal method that takes a reference.
GetLightSource can be const. Nothing calls DoubleClickHdl, remove it.

This a a prep-work for if and when we use gerrit
it is very important to call gerrit's commit-msg hook
and the sooner we teach our own hook to play nice with it
the less likely we will have issue during migration

This reverts commit 4001370b.

Conflicts:

	unusedcode.easy

It cannot be done at the main target, because there is no guarantee that
all help (or properties) files are in one directory.