overlay: Allow disabling secure playback

If the device's kernel isn't fully prepared for secure content
playback, having the secure field in the msm_rotator_img_info
struct will cause issues while playing out video.

The correct set of patches to the kernel (MDP, maybe vidc) needs
to be figured out for this to be enabled; to disable it,
add QCOM_NO_SECURE_PLAYBACK to the device's CFLAGS. (and remove
"secure" from msm_rotator_img_info)

Change-Id: Ib1d265133e66ae456c59a9f78b052a01cbd00116

Conflicts:
	liboverlay/overlayRotator.cpp
Older QCOM devices don't support OVERLAY_COMMIT

Amend: Fix tab conversion

Change-Id: I9241adef001f26fb7611623a23e05e559589532f

Conflicts:
	libexternal/external.cpp