issue #198 Test case for op_ret

tests/comptests/00_ret.lua

@@ -0,0 +1,10 @@
+f = compiler.load("return 1, 'hello', 5.6, true")
+assert(f and type(f) == 'function')
+local x = 4.3
+local a,b,c,d,e = f()
+assert(a == 1)
+assert(b == 'hello')
+assert(c == 5.6)
+assert(d == true)
+assert(x == 4.3)
+assert(e == nil)