samples: add Terra samples

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

samples/Terra/symbolvar4.t

@@ -0,0 +1,16 @@
+local a = symbol()
+local b = symbol(int)
+
+local c = symbol(int)
+local d = symbol()
+
+
+terra foo()
+	var [a],[b] = 1.25,1.25
+	var [c],[d] = 3.25,3.25
+	return [a] + [b] + [c] + [d]
+end
+
+local test = require("test")
+
+test.eq(foo(),8.50)