Also replace direct accesses into the type structure to get the return
type of a function with the same function.

Use it to retrieve statements contained in interface types.

Use it for retrieving the parent interface for interfaces.

Use it for retrieving the type that a pointer refers to.

Use it whenever retrieving the element type of an array.

Split out the defining of coclass types in the parser into a function.

It can trivially be derived from the type field now.

widl: Move creation of module type into a separate function, type_new_module and give it a special FC type.

Make duptype static and rename alias to type_new_alias.

Use type_is_alias to replace cumbersome "type->kind == TKIND_ALIAS" expressions.
Use type_get_real_type to simplify some code.

Store array type properties in the details union to save a bit of
memory and to make the general properties more obvious.