Add Qt5-specific flags to emulator builds

When building with Qt5 and for the emulator, set the build-time flags for
USE_KEY_FILTER and USE_MOUSE_FILTER.

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

Change-Id: If659cd99ac0cae03ec1fd58b84f7beea6c519d60
Reviewed-on: https://g2g.palm.com/1747
Reviewed-by: Build Verification
Reviewed-by: Eric Blade <eric.blade@palm.com>
Reviewed-by: Steve Lemke <steve.lemke@lge.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>
Tested-by: Roger Stringer <roger.stringer@lge.com>