samples: add Terra samples

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

samples/Terra/customtable.t

@@ -0,0 +1,10 @@
+
+
+struct A {
+}
+
+A.metamethods.__luametatable = { __index = function(self,idx) return 4 end }
+A.methods.foo = function() return 5 end
+a = terralib.new(A)
+
+assert(a.foo == 4)