samples: add Terra samples

source: https://github.com/zdevito/terra/tree/master/tests

samples/Terra/cunion.t

@@ -0,0 +1,34 @@
+local C = terralib.includecstring [[
+
+union testunion {
+  int idata;
+  float fdata;
+};
+
+typedef 
+	union {
+		int a;
+		float b;
+	} S;
+
+void setUnion(union testunion * u, S * s){
+  u->idata = 3;
+}
+int getUnionInt(union testunion * u){
+  return u->idata;
+}
+
+]]
+
+terra foo() : int
+  var u : C.testunion
+  C.setUnion(&u,nil)
+  var s : C.S
+  return C.getUnionInt(&u)
+end
+
+
+terralib.tree.printraw(C.S)
+
+local test = require("test")
+test.eq(foo(),3)