Revert "Add mouse wheel event handler to HostWindow"

This uses the wrong element in the SysMgrEvent structure

This reverts commit 2beb5d4fe9e3a4e349a4b904826a45a13e6f1938.

Open-webOS-DCO-1.0-Signed-off-by : Roger Stringer <roger.stringer@palm.com>

Change-Id: Ie2aff8a9bc2a72f3416a0ce61a5e8027f86abac1