nil value as gsub() 4th parameter

["Mauro Vezzosi"<mvezzosi@...>]

Hi

gsub() accepts an optional 4th parameter but it requires a not nil 
value for this parameter, if you pass it.
Could be a good idea, for the next Lua version, to change gsub() (and 
other functions ?) to accept a variable with nil value as 4th 
parameter ? (Like next() from Lua 3.2 to 4.0 Alpha)

Bye
Mauro