Fix opensuse powerpc build

I gave this code a spin on a G5 (PPC970) OpenSuse 10.3 system and
encountered same issues that should fix fot tyou next update.

The liburcu make system sis not set up for biarch (32-/64-bit) builds on
PPC. SLES10/OpenSUSE-10.3 is a default 32-bit, 64-bit capable system. To
build a 64-bit you need to insert -m64 for all compiles and link
operations. Also for 64-bit make install should move liburcu.so
to /usr/lib64 not /usr/lib. This is required to FSB complience. Is
worked around this by copying Makefile to Makefile64 and made the
required changes there.

For SLES11 we changed to to a 64-bit default and 32-bit capable system.
In either case you need to be able to build both 32-/64-bit liburcu.so
on same systems and need to insure that make install is appropriate.

Also I found that __SIZEOF_LONG__ was not defined and resulted in a
sigill on PPC64. I suspect this is XLC specific and you need solution
that works for GCC builds as well.

I have attached a patch that implement these change for your review.
With this patch I can build liburcu and run the tests successfully.

Finally when I build 32-bit (default for OpenSUSE 10) I get a unhandled
SIGUSER1. I ran out of weekend before I could figure that out.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>