[PATCH v6 0/7] MR1979: msvcrt: Remaining stubs for cm3

[Torge Matthies (＠tmatthies)]

Based on !2524.

This adds the remaining stubs needed for Crazy Machines 3 to work and decode preview images correctly in online mode.

--
  v6: msvcr100: Use Context blocking functions in reader_writer_lock class.
      msvcr100: Add ExternalContextBase::Unblock implementation.
      msvcr100: Add ExternalContextBase::IsSynchronouslyBlocked() implementation.
      msvcr100: Add ExternalContextBase::Block() implementation.
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/1979