Add test for combination of print() and tostring(), test case when tostring is changed in global environment.

src/test/res/print.lua

@@ -0,0 +1,26 @@
+-- print uses tostring under-the-hood!
+
+local function f()
+	print()
+	print('abc')
+	print(123)
+	print(true)
+	print('abc',123,true)
+end
+
+local function g()	
+	local fenv = {tostring=function(x)
+		return '*'..type(x)..'*'
+	end}
+	package.seeall(fenv)	
+	f()
+	print('setfenv', pcall(setfenv, 0, fenv), {}, f )
+	f()
+end
+
+local s,c = pcall( coroutine.create, g )
+print('create', s, s and type(c) or c)
+print('resume', pcall( coroutine.resume, c ) )
+f()
+
+