Implement parsing MultiProcessor tables, initializing APIC, initializing SMP, and port over the interrupt handling in Rust from eduOS-rs.

MAX_CORES is reduced to 256, because MultiProcessor tables don't support more than that.
entry.asm is relicensed to MIT just like the rest of the eduOS-rs and HermitCore Rust code.
Also improve debugging and make use of the or_else/unwrap_or_else Rust functions.

This is all untested work in progress! At least it compiles :)

Author: ColinFinck

arch/x86/kernel/entry.asm

@@ -898,7 +898,7 @@ void reschedule(void)
 	uint8_t flags;
 
 	flags = irq_nested_disable();
-	if ((stack = scheduler()))
-		switch_context(stack);
+	/*if ((stack = scheduler()))
+		switch_context(stack);*/
 	irq_nested_enable(flags);
 }