tuned;
more informative session result;
simplified signature (despite 448325de6e4f);
tuned -- nicer generated bash source;
clarified modules;
tuned whitespace;
more uniform signature for various process invocations; env refers to full environment, not the update;
more thorough cleanup -- in Scala;
clarified files; --HG-- rename : src/Pure/Concurrent/bash.ML => src/Pure/System/bash.ML rename : src/Pure/Concurrent/bash.scala => src/Pure/System/bash.scala rename : src/Pure/Concurrent/bash_windows.ML => src/Pure/System/bash_windows.ML