As glibc allocation routines are not re-entrant avoid calling delete in signal handler.
Instead the message send from the signal handler on process exit contains both the pid and the exit code. The internal _Process object always installs a data handler for the exit message and calls back into C++ to cleanup the resources allocated for running a process.
Changed the ActiveProcess (renamed to ProcessInfo) to form an explicitly linked list.
R=ager@google.com
BUG=dart:1
TEST=
Review URL: http://codereview.chromium.org//8227010
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@325 260f80e4-7a28-3924-810f-c04153c831b5
sgjesse@google.com