OLE32: Initialize RegisteredClass in CoRegisterClassObject

[Alex Villací­s Lasso]

This patch prevents a crash I experienced while investigating why native 
ODBC installed by MDAC_TYP.EXE fails to work correctly in fake Windows 
drive.

Changelog:
* Initialize (zero out) RegisteredClass in CoRegisterClassObject to 
prevent crash in CoRevokeClassObject when accessing (uninitialized) 
pMarshalledData