lowmemorykiller: also count zram swapfile usage

and tune LMK for use with compressed swap pages

Signed-off-by: Paul Reioux <reioux@gmail.com>

Conflicts:
	drivers/staging/android/lowmemorykiller.c

Conflicts:
	drivers/staging/android/lowmemorykiller.c

	modified:   drivers/staging/android/lowmemorykiller.c
Change-Id: I1415e40962e2e881b5c88e0996337c1799a2b2fa