frontend: force order of serialzation and literal phases in frontend

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
frontend: fix doc in serialization_phase

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: adds missing copyright info to serialization tests

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