[Issue 21142] New: TypeInfo_Class.offTi() not available via introspection

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21142

          Issue ID: 21142
           Summary: TypeInfo_Class.offTi() not available via introspection
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: andrei at erdani.com

(It's also undocumented?) There should be a way to obtain that info without
using the typeid, otherwise typeid cannot be implemented as a library.

This blocks https://github.com/dlang/druntime/pull/3174.

--