[Genie] Allow exit status to be set from init function
Submitted by Al Thomas
Currently an exit status of zero is always returned by a Genie program. To indicate a program has failed in some way a non-zero exit code would be useful, for example when using a Genie program from a Unix script.
At present init is a void function, so:
init return 1
gives "error: Return with value in void function"
The proposal is to make init return an integer, but for the parser to default to a value of zero if no return statement is provided. This maintains backwards compatibility.