Testsuite: assume timeout_prog always exists
Testsuite: assume timeout_prog always exists

Merge the following functions into one:
  * rawSystem
  * rawSystemWithTimeout
  * runCmd
  * runCmdFor
  * runCmdExitCode

I don't know why this wasn't done before.

sdiehl/ghc,olsner/ghc,sgillespie/ghc,ezyang/ghc,ezyang/ghc,snoyberg/ghc,olsner/ghc,ezyang/ghc,mettekou/ghc,vTurbine/ghc,snoyberg/ghc,mettekou/ghc,sgillespie/ghc,ezyang/ghc,shlevy/ghc,snoyberg/ghc,sdiehl/ghc,sdiehl/ghc,snoyberg/ghc,olsner/ghc,snoyberg/ghc,sdiehl/ghc,snoyberg/ghc,vTurbine/ghc,mettekou/ghc,mettekou/ghc,vTurbine/ghc,mettekou/ghc,sdiehl/ghc,sgillespie/ghc,shlevy/ghc,shlevy/ghc,shlevy/ghc,olsner/ghc,vTurbine/ghc,olsner/ghc,vTurbine/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,vTurbine/ghc,mettekou/ghc,shlevy/ghc,ezyang/ghc,olsner/ghc,vTurbine/ghc,shlevy/ghc,mettekou/ghc,sgillespie/ghc,olsner/ghc,sgillespie/ghc,snoyberg/ghc,sgillespie/ghc,sdiehl/ghc,sgillespie/ghc,sdiehl/ghc