When running --fork'ed, selectively mute some messages in child processes
(those messages that are expected to be printed by the main process as well,
such as on warning/error conditions that are almost certainly common to all
processes).
John's global variables exported from john.c to other source files (currently
this is just john_main_process).
Moved and renamed sig_pids from signals.[ch] to john_child_pids in john.[ch].
Introduced john_child_count.
Added john_main_process, john_child_count, and john_child_pids to best.c to
repair "make generic" builds, which were broken with recent commits
Node/fork/MPI fixes.
Merge branch 'master' into bleeding-jumbo

* master:
  Added john_main_process, john_child_count, and john_child_pids to best.c to repair "make generic" builds, which were broken with recent commits
  Moved and renamed sig_pids from signals.[ch] to john_child_pids in john.[ch]. Introduced john_child_count.
  John's global variables exported from john.c to other source files (currently this is just john_main_process).
  When running --fork'ed, selectively mute some messages in child processes (those messages that are expected to be printed by the main process as well, such as on warning/error conditions that are almost certainly common to all processes).

Conflicts:
	src/config.c
	src/external.c
	src/inc.c
	src/signals.c
	src/signals.h
	src/single.c
	src/wordlist.c
Post merge fixes. Some unifying of MPI vs. node/fork.