Fix FTBFS on ppc64

Patch provided by Aurelien Jarno <aurel32@debian.org> in
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=684470

dbus/sigsegv.c

@@ -107,7 +107,9 @@ static void signal_segv(int signum, siginfo_t* info, void*ptr) {
 #if !defined(__alpha__) && !defined(__ia64__) && !defined(__FreeBSD_kernel__) && !defined(__arm__) && !defined(__hppa__) && !defined(__sh__)
     for(i = 0; i < NGREG; i++)
         jack_error("reg[%02d]       = 0x" REGFORMAT, i, 
-#if defined(__powerpc__)
+#if defined(__powerpc64__)
+                ucontext->uc_mcontext.gp_regs[i]
+#elif defined(__powerpc__)
                 ucontext->uc_mcontext.uc_regs[i]
 #elif defined(__sparc__) && defined(__arch64__)
                 ucontext->uc_mcontext.mc_gregs[i]