widl: support ATTR_READONLY for interface properties

[Vincent Béron]

There are probably other easy ones like this one, but for now I only
need this one.

Huw, am I stepping on your toes?

Changelog:
Support ATTR_READONLY for interface properties.

Vincent
-------------- next part --------------
A non-text attachment was scrubbed...
Name: widl5.diff
Type: text/x-patch
Size: 699 bytes
Desc: not available
Url : http://www.winehq.org/pipermail/wine-patches/attachments/20050206/7fcdab80/widl5.bin