Shorthand lambda patches for lua 5.4 and 5.1

[Flemming Madsen <lua@...>]

I just made submissions for these on http://lua-users.org/wiki/LuaPowerPatches.

Search for "Shorthand lambdas"

Basically, the construction 

   |arglist| _expression_

is shorthand for 

   function(arglist) return _expression_ end

I have an accompanying patch for luacheck (https://github.com/mpeterv/luacheck), if anybody needs that.