Warn if C dependencies not found (kind of fixes #262)
Warn if C dependencies not found (kind of fixes #262)

This is just a basic check - generate a sample program and check if it compiles and links with relevant flags. Error messages (warning messages, 
actually) could use some improvement.

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