Overlay support for legacy camera libs

Move http://review.cyanogenmod.com/#/c/13285/ to proper place for
jellybean.

1. Rename OverlayHtc to Overlay in file names
2. Use BOARD_USES_LEGACY_OVERLAY to enable

Signed-off-by: Evan McClain <aeroevan@gmail.com>
Change-Id: Ib6afd1b610b1d3e263fcaa38585e7a1116baaf58