samples: add Terra samples

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

samples/Terra/pt.t

@@ -0,0 +1,18 @@
+
+
+local a = global(double)
+
+terra getptr()
+	return &a
+end
+
+local b = getptr()
+local c = terralib.pointertolightuserdata(b)
+print(b,c,a)
+
+terra foo(a : &&int)
+	
+end
+
+foo(c)
+print("DONE")