'cabal run': print a message before actually running the program.
'cabal run': print a message before actually running the program.

Fixes #1898.

Helkafen/cabal,thomie/cabal,beni55/cabal,mmakowski/cabal,garetxe/cabal,eric-stanley/cabal,sopvop/cabal,valderman/cabal,martinvlk/cabal,kosmikus/cabal,fugyk/cabal,typelead/epm,eric-stanley/cabal,gridaphobe/cabal,mightybyte/cabal,gridaphobe/cabal,enolan/cabal,Peaker/cabal,sopvop/cabal,themoritz/cabal,seereason/cabal,ian-ross/cabal,edsko/cabal,plumlife/cabal,gbaz/cabal,Helkafen/cabal,christiaanb/cabal,Heather/cabal,beni55/cabal,plow-technologies/cabal,seereason/cabal,kosmikus/cabal,valderman/cabal,kolmodin/cabal,fugyk/cabal,ian-ross/cabal,anton-dessiatov/cabal,mydaum/cabal,kolmodin/cabal,thoughtpolice/cabal,martinvlk/cabal,bennofs/cabal,trskop/cabal,triplepointfive/cabal,x-y-z/cabal,Peaker/cabal,bennofs/cabal,plumlife/cabal,corngood/cabal,anton-dessiatov/cabal,gbaz/cabal,x-y-z/cabal,lukexi/cabal,sopvop/cabal,rimmington/cabal,edsko/cabal,enolan/cabal,plow-technologies/cabal,thomie/cabal,trskop/cabal,mmakowski/cabal,ghc-android/cabal,mightybyte/cabal,garetxe/cabal,randen/cabal,themoritz/cabal,lukexi/cabal,triplepointfive/cabal,thoughtpolice/cabal,Heather/cabal,christiaanb/cabal,mydaum/cabal,randen/cabal,headprogrammingczar/cabal,typelead/epm,corngood/cabal,headprogrammingczar/cabal,rimmington/cabal,themoritz/cabal,ghc-android/cabal