[Windows] Explicit destroy WindowsLoopData after returning from message loop

[mzji]

i.e. Insert following code between line 260 and line 261 of file src/api/win32/mod.rs @ rev 3a013db :

                // Destroy window info. Causes deadlock in release build.
                WININFO_STASH.with(|stash| {
                    (*stash.borrow_mut()) = None;
                });