winreg: fix winreg_QueryValue IDL.
Note that before this change pidl generated code that just dereferenced size_is
and length_is values from unique pointers without checking whether these
pointers were actually NULL.
With this change, pidl now throws a warning like:
warning: Got pointer for `data_size', expected fully derefenced variable
which is not correct, probably because pidl does not evaluate the C expression.
Guenther
(cherry picked from commit
f258e98e177f0f75bab99654b9f32b10bb7ce37f)
(cherry picked from commit
f9a52643a5665efd5b11733179e574e3d0282e8b)