[GSoC - x86_64 port] Status update - June 21

[Amaan Cheval]

Hi!

In lieu of our weekly meeting, here's a quick status update. The past
week, I worked on:
- Making FreeBSD's bootloader load a custom ELF kernel, and then RTEMS
static binaries
- Fixing cpu.h up to reflect the x86_64 feature set
- Fixing the linker script up for my stub to allow for sysinit
functions to be included and called
- WIP: Context initialization and switching code

Next up (estimating 2 weeks until complete):
- Finish all of the RTEMS initialization required to get to bsp_start
successfully (for eg. it seems like sysinit calls filesystem
initialization routines, which I'm stubbing out for now, but will need
to implement to avoid having the testsuite end up throwing
"rtems_fatal_error_occurred".
- Port FreeBSD's console code to get to hello world with our stub

I'm aiming to get to a hacky working hello.exe as soon as possible,
and then we can work on making all the initialization routines, the
linker script. etc. be clean and perfectly correct instead of merely
functional in the emulator.

Cheers