Adding Julia and C++ examples

julia-to-rust/src/lib.rs

@@ -0,0 +1,4 @@
+#[no_mangle]
+pub extern fn double_input(input: i32) -> i32 {
+    input * 2
+}

julia-to-rust/src/main.jl

@@ -0,0 +1,7 @@
+input = Int32(10)
+output =  ccall((:double_input, "target/debug/libdouble_input"),
+                        Int32, (Int32,), input)
+
+print(input)
+print(" * 2 = ")
+println(output)