Proposal: POSIX process group API reform

[Favonia]

In light of the new functionality brought by getProcessGroupIDOf, I
would like to propose a more careful version of
interruptProcessGroupOf in process library which interrupts the
current process group of the target process, instead of using the
target process ID directly. The patch is here:
http://hackage.haskell.org/trac/ghc/ticket/5223 When the new version
of unix library is released, I will make a new patch to update .cabal
file as well (for the dependency on the unix library).

Simon: I am so grateful that you did the implementation of the future
API! I filed another bug to just fix some typos in it:
http://hackage.haskell.org/trac/ghc/ticket/5222