[CODE REORGANISATION] move st_object to its own .c/.h file and update Makefile

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
[CODE REORGANISATION] move def of struct st_object to its own .h file

Signed-off-by: etienne basset <etienne.basset@numericable.fr>
[DOC] Update COPYRIGHT and comments in st_scanf.c
Signed-off-by: etienne basset <etienne.basset@numericable.fr>