(x_to_w32_charset): Reinstall VIETNAMESE_CHARSET

(x_to_w32_charset): Reinstall VIETNAMESE_CHARSET
definition.
(w32_wnd_proc): Reinstall debugging output.
(w32_wnd_proc): Reinstall SetForegroundWindow change.
(syms_of_w32fns): Reinstall new initializer for
Vw32_phantom_key_code.

(x_to_w32_charset): Do partial matching of charset
names for most non-European charsets, to cope with wildcards or
missing spec dates.
(Fw32_send_sys_command): Post WM_SYSCOMMAND rather than sending it
to avoid deadlock when activating the menu bar.