To recap for people who find this: The problem occurs because of AIX's
extreme over-allocation and is specific to the 64-bit build.

Workarounds:

  1) Something like  ulimit -d 8000000.

  2) xlc: LDFLAGS="-L/usr/lib64 -q64 -bmaxdata:0x800000000" or
     LDFLAGS="-L/usr/lib64 -q64 -Wl,-bmaxdata:0x800000000".

     The first version seems more natural for xlc.

  3) gcc: LDFLAGS="-L/usr/lib64 -Wl,-bmaxdata:0x800000000 -maix64"



PSALLOC=early works really well for the libmpdec tests but is extremely
slow with the Python interpreter. Also, setting the environment in the
tests does not work.  It looks like it needs to be set before main()
starts.



So I'll just skip that test on AIX. It is not that important, and
the libmpdec maxprec tests, which are way more thorough, all pass
with PSALLOC=early.