Kernel: Implement barebones AML parser

This implements only parsing for AML in qemu. InvokeMethods are not
parsed since number of arguments to Methods is not yet known.

Parsing AML uses multiple kilobytes of stack space, so I increased
boot stack size by a lot :D

I am not sure where my own AML is going, but this is good start if
I decide to implement full ACPI on my own.

This code is very much just ugly macro expansion.

Qemu has 2 DefPackage elements that I am not able to parse. Package
data ends while there should be still multiple elements.

kernel/arch/x86_64/boot.S

@@ -54,7 +54,7 @@ bananboot_end:
 
 .section .bss, "aw", @nobits
 	boot_stack_bottom:
-		.skip 4096 * 4
+		.skip 4096 * 64
 	boot_stack_top:
 
 	.global g_kernel_cmdline