samples: add Terra samples

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

samples/Terra/nestextract.t

@@ -0,0 +1,40 @@
+
+
+struct A {
+	a : int
+}
+
+count = global(int,0)
+
+terra twoAs(a : int)
+	return A {a}, A { a }
+end
+
+function A.metamethods.__cast(fromt,tot,exp)
+	if tot == A and fromt == int then
+		return `twoAs(exp)._0
+	end
+	error("what")
+end
+
+terra twoInts()
+	count = count + 1
+	return count,2
+end
+
+terra takesAnA(a : A)
+	return a.a
+end
+
+dotwice = macro(function(exp)
+	return {exp,exp}
+end)
+
+terra doit()
+	return dotwice(takesAnA((twoInts()._0))) 
+end
+
+
+doit:printpretty()
+local test = require("test")
+test.meq({1,2},doit())