samples: add Terra samples

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

samples/Terra/stattest.t

@@ -0,0 +1,13 @@
+local ffi = require("ffi")
+if ffi.os == "Windows" then
+  return
+end
+
+C,T = terralib.includec("sys/stat.h")
+terra dostat()
+	var s : T.stat
+	C.stat("stattest.t",&s)
+	return s.st_size
+end
+
+assert(dostat() == 210)