[PATCH] Add biarch support for powerpc64

[Roland McGrath]

Is there any actual benefit to arch=powerpc64 and the separate directory of
files that all just #include the powerpc files?  I think we'd do as well
just to leave arch=powerpc for the powerpc64 configuration.  It doesn't
seem likely that these lists will diverge for ppc32/ppc64 in the future.

It's fine enough to use a < 0 test for the MSR, where we're testing the
high bit because that happens to be the relevant flag.  But it merits a
comment that this constitutes a test of the MSR_SF_LG bit.

I haven't really checked over all the individual biarch cases or potential
needs for them.  They look fine and I assume you've checked the details.

For NEWS and the like we should make clear that this only permits a ppc64
build of strace to handle ppc32 tracees, not vice versa.  This is exactly
equivalent to the situation on x86_64/i386, but the context may differ.
That is, there are powerpc systems where it's normal to have most of
userland (including strace) be ppc32 and only the kernel and some userland
things be ppc64.  To support those systems more smoothly, we could also
make ppc32 strace use PTRACE_GETREGS64 to support ppc64 tracees, but that
would require much more work in the inverse biarch decoding support.


Thanks,
Roland