Add explicit padding fields in the corresponding structures.

This is similar to 0bdab5f8.

d3d9: Use separate codepaths for failure and NULL return values in GetVertexShader() / GetPixelShader().

It's only used for shader_hw_map2gl() and vshader_hw_rsq_rcp(), and we
can handle those the same way we handle the GLSL equivalents.

widl: Write the local stubs file based on the parsed list of statements, rather than using hooks in the parser code.

widl: Write the generated file containing IID, DIID, CLSID and LIBID data based on the parsed list of statements instead of using hooks in the parser code.

widl: Write the typelib based on the statement list generated in the typelib_t object instead of using hooks in the parser code.

Set the details of the structure to the previously defined version if
available, or add it to a list of incomplete types otherwise. Only set
the defined flag when the structure is actually defined in the IDL
file so that the type is written out in the exact order that it is
mentioned in the file.