Use C for syscalls

src/sys.rs

@@ -0,0 +1,16 @@
+#[link(name = "syscalls")]
+extern "C" {
+    pub fn start_window_draw();
+
+    pub fn end_window_draw();
+
+    #[link_name = "exit0"]
+    pub fn exit() -> !;
+
+    pub fn define_window(ebx: u32, ecx: u32, edx: u32, edi: u32);
+    pub fn display_message(ebx: u32, ecx: u32, edx: u32, edi: u32, esi: u32);
+
+    pub fn wait_event() -> u32;
+
+    pub fn pressed_key() -> u32;
+}