lib/kernel: introduce SELF type in Object

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: test the virtual type SELF

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib/android: remove all custom SELF types

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib/c&java: remove all custom SELF types

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib/trees: rename SELF virtual type to N

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>