android_pipe: import the qemu_pipe/goldfish_pipe code

This brings in the android emulator pipe code from the current aosp-qemu
master branch. So far it's just a comment and hack to get compiling
change:

  - remove dependency on android utils (ANEW/ASTRDUP/AFREE)
  - detach from the goldfish_device bus bits (inc irq raising)
  - import a few helper functions (uint64_set_high/low, goldfish_guest_is_64bit)
  - disable the VM save/restore code
  - use current_cpu for memory translation ops instead of cpu_single_env

What's left to do:

  - properly QOMify with SYS_BUS_DEVICE et al
  - somehow map into DT or some-such other emulator to guest mapping
  - figure out how IRQs are going to be raised
  - and testing etc...