examples/yield: document --bench required option
examples/yield: document --bench required option

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