samples: add Terra samples

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

samples/Terra/cstruct.t

@@ -0,0 +1,20 @@
+local C = terralib.includecstring [[
+
+struct teststruct {
+  int idata;
+  float fdata;
+};
+
+void makeitlive(struct teststruct * s) {}
+
+]]
+
+
+terra foo()
+	var a : C.teststruct
+	a.idata = 3
+	a.fdata = 3.5
+	return a.idata + a.fdata
+end
+
+assert(foo() == 6.5)