fix Issue 13084 - ModuleInfo.opApply delegate expects immutable parameter

- cast to mutable
deprecate mutating assignment to ModuleInfo

- It's not possible to deprecate default construction
  as `deprecate this()` is not allowed.

- Deprecating copy-construction `deprecate this(this)`
  results in a lot of false deprecation warnings
  due to compiler generated functions.
Merge pull request #909 from MartinNowak/fix13084

fix Issue 13084 - ModuleInfo.opApply delegate expects immutable parameter