xserver-xorg 1.7.4,1.8.0,git : make it MACHINE_ARCH for ion and bump PR

xserver-xorg 1.7.4,1.8.0,git : make it MACHINE_ARCH for ion and bump PR

In case of ion(a machine),Xorg is configured with --enable-xinerama,
  But xorg is not MACHINE_ARCH anymore,so that's problematic.
  The easiest fix as suggested in #oe is this one:
    <XorA> needs PACKAGE_ARCH_ion = "${MACHINE_ARCH}" then
PR was also bumped(advise taken in #oe):
  <GNUtoo> I'll also bump PR: PR = "${INC_PR}.0" => PR = "${INC_PR}.1"
  <GNUtoo> JaMa, is it ok to bump like this for xserver or does every xf86-somesystem-somedriver has to be rebuilt?
  <JaMa> GNUtoo: no, it should be fine..
  <GNUtoo> ok thanks a lot
  <JaMa> drivers needs to be bumped only if ABI changed