mathlib

86d0f292 - refactor(*): make `is_group_hom` extend `is_mul_hom` (#1214)

refactor(*): make `is_group_hom` extend `is_mul_hom` (#1214) * map_mul/map_add: use explicit parameters Preparing to merge `is_mul_hom` with `is_group_hom` * make `is_group_hom` extend `is_mul_hom`, adjust many proof terms * Add a comment