Add a -betterC test for std.typecons.Tuple

Author: wilzbach

test/betterC/typecons.d

@@ -0,0 +1,7 @@
+extern(C) void main()
+{
+    import std.typecons;
+    auto t = tuple(1, 2);
+    assert(t == tuple(1, 2));
+    auto t3 = tuple(1, 'd');
+}