buildroot

live555: use upstream install target for staging installation

Move include directories out of $(STAGING_DIR)/usr/include/live. This is
upstream choice, and is consistent with e.g. Debian. Update mplayer and vlc to
match.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>