for empty install plans, print the packages that are installed
for empty install plans, print the packages that are installed

This is a fix for #623.

If we ask to install a package without --reinstall that's already
there, then we'll show the package and its version in the warning
message and suggest the use of the --reinstall flag.

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