build-kernel.sh: Make --arch=arm64 build ranchu version by default.

This patch modifies build-kernel.sh to use the 'ranchu' defconfig
by default with using --arch=arm64. This corresponds to the virtual
ARM64 board supported by the qemu-android [1], not the Android
emulator.

This will allow us to get rid of the special kernel fork at [2]

+ Changes the way generated kernel images are named. By default,
  they now go into /tmp/kernel-qemu/<arch>-<kernel_version>/
  and are simply named kernel-qemu and vmlinux-qemu, as expected
  by the platform build and the emulator (when placed under
  $AOSP/prebuilts/qemu-kernel/)

  Deal with the special case of ARMv7 which requires an -armv7
  suffix, to differentiate with ARMv5 kernel images, for legacy
  reasons.

Tested with the following combinations:

  android-goldfish-3.4:  arm, x86, mips
  android-goldfish-3.10: x86, x86_64, arm64

BUG=16540589

[1] https://qemu-android.googlesource.com/qemu-android
[2] https://qemu-android.googlesource.com/kernel

Change-Id: I0016acc5879b7e7f6233b8d9acd170b2ec00370f
Merge "build-kernel.sh: Make --arch=arm64 build ranchu version by default."
Fixed network access in windows emulator

When we switched to MinGW gcc 4.8.3, guests became unable to access
the network.

It turns out that gcc packs C bit fields differently on Windows than
on other platforms.  This change declares structures in a way that
works across all platforms.

Change-Id: Iba976902fedccc1fc5cf9400f71e71e7d253da8b
Merge "Fixed network access in windows emulator"