v2.0.1

• Optimize mutations of objects to its own type (not necessarily noop since mixin can be touched in this case)
• Add gradual_mutation::cancel
• type::buf_size to public member
• g::get_mixin_info for const mixin types
• Fix several (mostly benign) instances of UB
• v1compat:
  • Set mixin names from typeid (as it was the case in v1)
  • Fix message string names
  • Split mutation dependent_mixins into two to account for simplified rules