samples: add Terra samples

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

samples/Terra/constructor.t

@@ -0,0 +1,12 @@
+
+local b = 1
+local dd = "d"
+local c = symbol()
+
+terra foo()
+	var a = { _0 = [b], [c] = 2, [dd] = 3, r = 4}
+	return a._0 + a.[c] + a.d + a.r
+end
+
+local test = require("test")
+test.eq(foo(),10)