Add wxThread::MSWGetHandle().

Under MSW a thread has both an ID, returned by wxThread::GetId(), and a
handle, which couldn't be retrieved so far. Add an accessor to do it.

Closes #16170.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76418 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/thread.h

@@ -583,6 +583,11 @@ public:
     // identifies a thread inside a process
     wxThreadIdType GetId() const;
 
+#ifdef __WINDOWS__
+    // Get the internal OS handle
+    WXHANDLE MSWGetHandle() const;
+#endif // __WINDOWS__
+
     wxThreadKind GetKind() const
         { return m_isDetached ? wxTHREAD_DETACHED : wxTHREAD_JOINABLE; }