bug fixes and simplifications. Refs: #104.
- hwnd was an undefined variable in Open.
- the waste of static variable memory has been avoided.
- the stackSize is set to 16KB.
- waiting for callNameTaken can no longer result in an endless loop if thread creation fails.
- Dialog.IsWine() not be called inside a thread.
- DuplicateHandle removed.
- CloseHandle called for thread handle.
- many variables were essentially unused and have been removed.

Signed-off-by: Josef Templ <josef.templ@gmail.com>