Fix File.set_length return value in success.
Fix File.set_length return value in success.

Perelandric/ponyc,ponylang/ponyc,ryanai3/ponyc,jemc/ponyc,dipinhora/ponyc,jupvfranco/ponyc,dipinhora/ponyc,jupvfranco/ponyc,cquinn/ponyc,mkfifo/ponyc,Praetonus/ponyc,mkfifo/ponyc,kulibali/ponyc,Perelandric/ponyc,ponylang/ponyc,malthe/ponyc,cquinn/ponyc,Perelandric/ponyc,malthe/ponyc,kulibali/ponyc,boemmels/ponyc,Theodus/ponyc,Perelandric/ponyc,Perelandric/ponyc,dipinhora/ponyc,jupvfranco/ponyc,ryanai3/ponyc,Praetonus/ponyc,lukecheeseman/ponyta,jupvfranco/ponyc,CausalityLtd/ponyc,Theodus/ponyc,boemmels/ponyc,mkfifo/ponyc,mkfifo/ponyc,Theodus/ponyc,malthe/ponyc,doublec/ponyc,Praetonus/ponyc,sgebbie/ponyc,cquinn/ponyc,sgebbie/ponyc,malthe/ponyc,doublec/ponyc,mkfifo/ponyc,CausalityLtd/ponyc,doublec/ponyc,lukecheeseman/ponyta,kulibali/ponyc,ryanai3/ponyc,CausalityLtd/ponyc,jemc/ponyc,boemmels/ponyc,lukecheeseman/ponyta,jemc/ponyc,ponylang/ponyc,jupvfranco/ponyc,sgebbie/ponyc,sgebbie/ponyc,boemmels/ponyc,Theodus/ponyc,Theodus/ponyc,cquinn/ponyc,kulibali/ponyc,sgebbie/ponyc,Praetonus/ponyc,boemmels/ponyc