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: I8436a55bf4b69ed94672d9819d7d541f33677207