meta-android: abootimg: add native variant

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-android: kernel_android.bbclass: use abootimg instead of mkbootimg

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-android: android-tools: add make_ext4fs

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-android: classes: add bbclass to generate a fastboot flashable image

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-samsung: conf: machine: tuna: add board specific system partition size

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-asus: conf: machine: grouper: add board specific system partition size

Signed-off-by: Simon Busch <morphis@gravedo.de>
meta-acer: conf: machine: a500: add board specific system partition size

Signed-off-by: Simon Busch <morphis@gravedo.de>