[x86] Add decode assist capability check.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>
[x86] Supports BIOS boot till the protected mode.

o Let the BIOS boot up till enabling and executing
  code in protected mode.
o Added handle for CPUID intercept.
o Added x86 info struct to vcpu structure.
o Guest instruction decoding.
o Realmode guest paging.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>
[Emulators] NS16550 Compliant UART Emulator.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>
[x86] Seabios debug prints on emulated UART

o With NS16550 provided to guest, the seabios is
  able to boot and print using the emulated uart.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>
[x86] Some compilation warning fixes.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>
[EMULATORS] Compilation warning fix in ns16550 emulator.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>
[x86] Fix boot table aliased mappings

o Current implementation used to use the same
  page for all the mappings.
o Major problem was the VGA mappings which used
  to alias to code mappings as the code used to
  grow.
o Multiple pages are now used and mapped accordingly.

Signed-off-by: Himanshu Chauhan <hschauhan@nulltrace.org>