My message queue patch fixes the 64 bits -> 32 bits conversion of
siginfo, but didn't change the 32 -> 64 bits conversion done in
sys32_rt_sigqueueinfo() which was apparently bogus as well.

After much discussion & debate on the right way of converting that
structure, I decided to go the sparc64 / s390 way, and not the x86_64
way, that is to copy the various unions data "as is". This guarantees
that whatever a 32 bist app passes there, another 32 bits app will
understand it. Crossover between 32 and 64 bits apps on such things
as home-made userland siginfo isn't something we can help with anyway.

The x86_64 choice of converting as if it was an RT signal, thus
converting the sigval, cannot easily be applied to big endian archs
since the sigval is a union of a ptr and an int, on BE, the int
happens to be on the wrong half of the 64 bits ptr, thus  we can't
do a simple conversion.