widl: Allow pointers, type-qualifiers and other more complicated constructions in sizeof and cast expressions.

Make it return the var_t object rather than making the callers dig it
out, and make it take the attributes list so that callers don't have
to set it.

The range will not be verified in and misconception could turn into a
security problem.

Move [string] attribute validation from reg_typedefs to set_type.

This reverts commit e4e21193.

The IDBProperties test shows that this special case is not needed to
for these types to be marshalled correctly.

Spotted by Christian Costa.

richedit: When inserting an OLE object from an RTF stream, don't force update as the stream is not fully read.