samples: add Terra samples

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

samples/Terra/simpleapply.t

@@ -0,0 +1,19 @@
+struct Vec { data : int[4] }
+Vec.metamethods.__apply = terra(self : &Vec, i : int)
+    return self.data[i]
+end
+
+struct Vec2 { data : int[4] }
+Vec2.metamethods.__apply = macro(function(self,b)
+    return `self.data[b]
+end)
+
+terra bar()
+    var a = Vec { array(1,2,3,4) }
+    var b = Vec2 { array(1,2,3,4) }
+    b(2) = b(2) + 1
+    return b(2) + a(2)
+end
+
+local test = require("test")
+test.eq(bar(),7)