Potential Mono removal from 32-bit big endian PowerPC in next upload

[Jo Shields <directhex@apebox.org>]

Dear PPC porter people,

The major Mono version pending in experimental fixes GCC5 and fixes 
reproducible builds and a dozen other bugs, so I don't want to delay it.

It doesn't build on PowerPC any more, and nobody upstream is working on it.

We recently introduced ppc64el, which is working, but there's nobody who 
cares about 32-bit BE - the community contributor who gave us our 
ppc64el port is working on ppc64, but simply isn't interested in 32-bit.

I've fixed up the build such that there is a single failure, a single 
assert, still breaking the build (and about 31 of the tests in the 
runtime test suite): 
https://gist.githubusercontent.com/directhex/f890350006e72be706af/raw/2bae2f1ea487f4f6c6f7d5ccb256feda35627c28/assert

This state of the art (which contains patches beyond what is in 
Experimental) is at https://github.com/directhex/mono-1/tree/ppc32

I've hit the limits of my ability to debug and fix. I need someone 
familiar with PPC porting to tell me what magic switch to flip to repair 
it, within a short period of time - otherwise I'll be foced to simply 
mark 32-bit BE powerpc as a dead arch & stop trying to support it in 
Mono and its 100 related packages.

Thanks.

--Jo