Bustage fix, don't enable MOZ_IPC for PPC builds.

configure.in

@@ -5469,6 +5469,9 @@ dnl ========================================================
 dnl = Disable IPC support for tabs and plugins
 dnl ========================================================
 case "${target}" in
+powerpc-apple-darwin*)
+    MOZ_IPC=
+    ;;
 *-wince*)
     MOZ_IPC=
     ;;