Stupid me. How could I have prevented that? Is there some sort of 'Code of Ethics' of the WINE project that I should have read before and that tells me not to debug a binary from MS in order to improve a WINE implementation?
It's on the Developers' FAQ on the wiki: http://wiki.winehq.org/DeveloperFaq#head-fed5011434f62ae1a88baebfb8193a37ea7...
I admit the warning is pretty well buried. It's been discussed here on wine-devel on several occasions, searching for "wine disassembly' will produce one such thread. --Juan