Initial patch to implement 'defer' statement in Lua 5.4

patches/README.md

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+These patches are for Lua 5.3 and 5.4.
+
+The 'defer' patch adds the defer statement to Lua.
+
+Note that in Lua 5.4 a deferred closure may be called more than once just as the close method of a to-be-closed variable 
+may be called more than once, when exiting the scope. I am checking why Lua 5.4 behaves this way.