x64: function calls; http: download_file()

examples/x64/hello_world.v

@@ -1,6 +1,11 @@
 fn main() {
+	println('x64 test')
 	for _ in 0..5 {
 		println('Hello world from V x64 machine code generator!')
 	}
 	println('Hello again!')
 }
+
+fn test_fn() {
+	println('test fn')
+}