KEY_HOME is the key to go back to the beginning of the line, not the key to
get into an overview mode, as Windows does. GNOME can already make use of
the Windows key on multiple form factors, and other desktop environments
can use it depending on the form factor.

Using "Windows" as the emitted key also means that the keycode sent out
matches the symbol on the key itself.

So switch KEY_HOME to KEY_LEFTMETA ("Windows" key).
Signed-off-by: Bastien Nocera <hadess@hadess.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>