Hello, I'm writer for past patch.
3.4-issue21085-struct_siginfo.patch removes si_band field from struct_siginfo if the C siginfo_t doesn't have si_band field.
This modification raises a incompatibility between platforms having struct_siginfo.
Now, I wrote another patch that doesn't change fields of struct_siginfo to avoid its incompatibility. 
And I built cpython 3.5.2+ on vista cygwin-x86 using this patch.
Murray, would you be able to tell me your idea?
Many thanks.

New patch changes:
If platform has the C siginfo_t structure, but it doesn't have si_band field, the struct_siginfo.si_band field is always assigned zero at function return value.