samples: add Terra samples

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

samples/Terra/exittest.t

@@ -0,0 +1,9 @@
+
+C = { exit = terralib.externfunction("exit", int -> {}) }
+
+
+terra moo()
+    C.exit(0)
+end
+
+moo()