Rationale

- Remove S12.2-6 (covered in A781). - Change S11 to S50, S12.1 to S51.1, S13 to S52, S14 to S10 and S15 to S11 (consistency with A781 for supplementary requirements and A744 revision). - Change CGMMN to CG6MMnN to be consistent with alloy designations (A781 X1).