Renamed Machine::init_machine and fixed stack overflow by allocating main_memory to the heap

src/main.rs

@@ -6,6 +6,6 @@ use kernel::system::System;
 use simulator::machine::Machine;
 
 fn main() {
-    let machine = Machine::_init_machine();
+    let machine = Machine::init_machine();
     let _system = System::new(machine);
 }