samples: add Terra samples

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

samples/Terra/quote3.t

@@ -0,0 +1,13 @@
+c = global(0)
+terra count()
+    c = c + 1
+    return c
+end
+foo = macro(function(a,b) return `a + a + a + b + count() end)
+terra doit()
+    var a = -100
+    return foo(count(),4)
+end
+
+local test = require("test")
+test.eq(doit(),14)