samples: add Terra samples

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

samples/Terra/setter.t

@@ -0,0 +1,39 @@
+
+struct A {
+a : int;
+b : int;
+}
+
+terra A.metamethods.__update(self : &A, a : int, b : int)
+    self.a = a
+    self.b = b
+end
+terra A.metamethods.__apply(self : &A, a : int)
+    return a + self.b
+end
+
+struct B {
+    a : int
+}
+
+
+B.metamethods.__update = macro(function(me,arg,arg2,rhs)
+    return quote me.a = arg + arg2 + rhs end
+end)
+
+B.metamethods.__setentry = macro(function(field,self,rhs)
+    field = field:sub(2)
+    return quote self.[field] = self.[field] + rhs end
+end)
+
+terra foo()
+    var a : A
+    a(4) = 5
+    var b : B
+    b(3,4) = 5
+    b._a = 1
+    return a.a + a.b + a(3) + b.a
+end
+
+--foo:printpretty()
+assert(foo() == 9+8+3+4+5+1)