[status report #11 - #13] BHyVe BIOS emulation to boot legacy systems

[Takuya ASADA]

* project summary
The project goal is to support BIOS emulation on BHyVe, enabling boot
from disk image.
I going to focus booting FreeBSD/amd64 from disk image on this GSoC,
but final goal is to make BHyVe able to support more guest OSes.

* porting "doscmd" a DOS emulator to BHyVe, as a BIOS emulation library #3
Now all bios call, creating interrupt vector and it's trampoline code,
some io port emulation is handled by libbiosemul.
Also I added handling secondary PIC IO(0xa0, 0xa1), keyboard
controller IO(0x60, 0x64), which used by boot1/btx.
svn diff -r240550:240565
https://socsvn.freebsd.org/socsvn/soc2012/syuu/bhyve-bios

In result, it could passed MBR stage and boot1, now get into btx stage.