Open an input method.
function opens an input method whose language and name match
and returns a pointer to the input method object newly allocated.
This function at first decides a driver for the input method as described below.
the driver pointed by the variable
has the property
the driver pointed to by the property value is used to open the input method. If
has no such a property,
Then, the member
of the driver is called.
is set in the member
of the structure
so that the driver can refer to it.