Fixed the previous commit: All lists of Strings in package configuration files
were split at commas to allow list-based variables, but this broke perfectly
sensible things like

   ["-Wl,-rpath,/usr/lib/jvm-bridge/lib/"]

into

   ["-Wl","-rpath","/usr/lib/jvm-bridge/lib/"]

which is plainly wrong. Now we do this *only* when a variable occurs on its own,
like:

   ["${deps}","foo"] => ["base","haskell98","network","foo"]

I have slight doubts about this obscure feature, but Sigbjorn seems to want
it...

Merge to STABLE