widl: Use 'class' for coclass typedefs in C++.

[Thomas Faber]

This fixes a warning when using widl-generated headers from C++ with MSVC:
warning C4099: 'Xxx' : type name first seen using 'struct' now seen using 'class'

This is equivalent to what midl generates for the same situation.
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: 0001-widl-Use-class-for-coclass-typedefs-in-C.patch
URL: <http://www.winehq.org/pipermail/wine-patches/attachments/20121014/326a9f18/attachment.ksh>