samples: add Terra samples

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

samples/Terra/typeexp.t

@@ -0,0 +1,9 @@
+atype = int
+terra foo(a : atype)
+   var b : &atype = &a
+   return @b
+end
+
+local test = require("test")
+
+test.eq(foo(3),3)