samples: add Terra samples

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

samples/Terra/vtablerec.t

@@ -0,0 +1,30 @@
+
+struct V {
+	entry : {&A} -> {}
+} and
+struct A {
+	vtable : &V
+}
+
+terra what(a : &A) : {}
+end
+
+what:compile()
+
+terra bar()
+	var v : V
+	v.entry = what
+end
+
+bar:compile()
+
+--[[
+{&A}->{}
+&A
+A
+&V
+V
+&{&A}->{}
+{&A}->{}
+
+]]