Added Rust to C++ example

rust-to-cpp/src/main.rs

@@ -0,0 +1,11 @@
+extern crate libc;
+
+extern {
+    fn triple_input(input: libc::c_int) -> libc::c_int;
+}
+
+fn main() {
+    let input = 4;
+    let output = unsafe { triple_input(input) };
+    println!("{} * 3 = {}", input, output);
+}

rust-to-cpp/src/triple.cpp

@@ -0,0 +1,4 @@
+extern "C"
+int triple_input(int input) {
+    return input * 3;
+}