Allow return without expression

[skasti]

Small change to allow writing return #5070 instead of return [#5070] and similar.
Still allows the old way of returning only using expressions, but I find this syntax less error-prone.

Also explicitly setting _value to 0 if no value is returned, as I have had some confusion where I get a unexpected _value but _value_returned is 0 😅

[terjeio]

This is a breaking change? Returning an explicit value with e.g. return [123.456] will no longer work?
I am currently without access to a controller so cannot check.

FYI I am going to add expresssion support to ENDSUB and clearing of _value and _value_returned on CALL since these were not in compliance with the LinuxCNC spec.

[skasti]

This is a breaking change? Returning an explicit value with e.g. return [123.456] will no longer work? I am currently without access to a controller so cannot check.

No, it just means you can use any of:

return 1
return [1]
return #5070
return [#<something>+10]
etc

FYI I am going to add expresssion support to ENDSUB and clearing of _value and _value_returned on CALL since these were not in compliance with the LinuxCNC spec.

I don't think I understand. Will read again tomorrow and see if brain is braining :P