Support for UEFI BIOS

Hi there,

I made an attempt to boot using a uefi bios and failed. I'd loved to see uefi support so I can demo a personal project on a webpage.

I attempted to boot using a prebuilt ia32 uefi package from here https://www.kraxel.org/repos/jenkins/edk2/

I unpacked the files like so
```
ymir:foo$ rpm2cpio edk2.git-ovmf-ia32-0-20181129.806.ga5274cdc87.noarch.rpm | cpio -idmv
./usr/share/doc/edk2.git-ovmf-ia32
./usr/share/doc/edk2.git-ovmf-ia32/README
./usr/share/edk2.git
./usr/share/edk2.git/ovmf-ia32
./usr/share/edk2.git/ovmf-ia32/OVMF-need-smm.fd
./usr/share/edk2.git/ovmf-ia32/OVMF-pure-efi.fd
./usr/share/edk2.git/ovmf-ia32/OVMF-with-csm.fd
./usr/share/edk2.git/ovmf-ia32/OVMF_CODE-need-smm.fd
./usr/share/edk2.git/ovmf-ia32/OVMF_CODE-pure-efi.fd
./usr/share/edk2.git/ovmf-ia32/OVMF_CODE-with-csm.fd
./usr/share/edk2.git/ovmf-ia32/OVMF_VARS-need-smm.fd
./usr/share/edk2.git/ovmf-ia32/OVMF_VARS-pure-efi.fd
./usr/share/edk2.git/ovmf-ia32/OVMF_VARS-with-csm.fd
./usr/share/edk2.git/ovmf-ia32/UefiShell.iso
29490 blocks
```

Then moved the UEFI binary & iso in v86
```
ymir:foo$ cp usr/share/edk2.git/ovmf-ia32/OVMF-pure-efi.fd ../v86/bios/
ymir:foo$ cp usr/share/edk2.git/ovmf-ia32/UefiShell.iso ../v86/images/
```
I made these changes to basic.html to point to the uefi bios & iso.
```
--- a/examples/basic.html
+++ b/examples/basic.html
@@ -12,13 +12,10 @@ window.onload = function()
vga_memory_size: 2 * 1024 * 1024,
screen_container: document.getElementById("screen_container"),
bios: {
- url: "../bios/seabios.bin",
- },
- vga_bios: {
- url: "../bios/vgabios.bin",
+ url: "../bios/OVMF-pure-efi.fd",
},
cdrom: {
- url: "../images/linux.iso",
+ url: "../images/UefiShell.iso",
},
autostart: true,
});
```

The last step were `make run` and finally navigated to http://127.0.0.1:8000/examples/basic.html only to see black screen and no output. I also tried leaving the vga bios in place.

Note I can boot into the uefi shell with `qemu-system-i386 -bios bios/OVMF.fd -cdrom images/UefiShell.iso`

Cheers, Jon