[PATCH v2 0/2] MR10636: msvcp140: Implement basic_istream<char> move assignment.

[Theodoros Chatzigiannakis (＠TChatzigiannakis)]

This MR implements a missing operator that is invoked by Native Instruments Kontakt Player (and likely the full Kontakt too).

---

_Disclaimers for reviewers:_

* _AI was used while tracking down the issue and coming up with the fix._
* _I am not affiliated with Native Instruments, I'm just a user._

--
  v2: msvcp140: Implement basic_istream<char> move assignment.
      msvcp140/tests: Add basic_istream<char> move assignment tests.
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10636