i386: hvf: add code base from Google's QEMU repository

This file begins tracking the files that will be the code base for HVF
support in QEMU. This code base is part of Google's QEMU version of
their Android emulator, and can be found at
https://android.googlesource.com/platform/external/qemu/+/emu-master-dev

This code is based on Veertu Inc's vdhh (Veertu Desktop Hosted
Hypervisor), found at https://github.com/veertuinc/vdhh

. Everything is
appropriately licensed under GPL v2-or-later, except for the code inside
x86_task.c and x86_task.h, which, deriving from KVM (the Linux kernel),
is licensed GPL v2-only.

This code base already implements a very great deal of functionality,
although Google's version removed from Vertuu's the support for APIC
page and hyperv-related stuff. According to the Android Emulator Release
Notes, Revision 26.1.3 (August 2017), "Hypervisor.framework is now
enabled by default on macOS for 32-bit x86 images to improve performance
and macOS compatibility", although we better use with caution for, as the
same Revision warns us, "If you experience issues with it specifically,
please file a bug report...". The code hasn't seen much update in the
last 5 months, so I think that we can further develop the code with
occasional visiting Google's repository to see if there has been any
update.

On top of Google's code, the following changes were made:

- add code to the configure script to support the --enable-hvf argument.
If the OS is Darwin, it checks for presence of HVF in the system. The
patch also adds strings related to HVF in the file qemu-options.hx.
QEMU will only support the modern syntax style '-M accel=hvf' no enable
hvf; the legacy '-enable-hvf' will not be supported.

- fix styling issues

- add glue code to cpus.c

- move HVFX86EmulatorState field to CPUX86State, changing the
the emulation functions to have a parameter with signature 'CPUX86State *'
instead of 'CPUState *' so we don't have to get the 'env'.

Signed-off-by: Sergio Andres Gomez Del Real <Sergio.G.DelReal@gmail.com>
Message-Id: <20170913090522.4022-2-Sergio.G.DelReal@gmail.com>
Message-Id: <20170913090522.4022-3-Sergio.G.DelReal@gmail.com>
Message-Id: <20170913090522.4022-5-Sergio.G.DelReal@gmail.com>
Message-Id: <20170913090522.4022-6-Sergio.G.DelReal@gmail.com>
Message-Id: <20170905035457.3753-7-Sergio.G.DelReal@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>