More corrections w.r.t. process groups

To accompany r31092 and r310924, also ensure to create a new process
group in the child right after the orted forks.  Add trivial configury
to ensure that we have setpgid, and only do the setpgid/getpgid if we
have setpgid.

Without this commit, killing the entire process group can do
unexpected things (e.g., kill the orted, mpirun, and even mpirun's
parent!).

cmr=v1.7.5:reviewer=rhc

This commit was SVN r31132.

The following SVN revision numbers were found above:
  r31092 --> open-mpi/ompi@99c9ecaed0

The following SVN revisions from the original message are invalid or
inconsistent and therefore were not cross-referenced:
  r310924

configure.ac

@@ -854,7 +854,7 @@ OMPI_CHECK_FUNC_LIB([dirname], [gen])
 # Darwin doesn't need -lm, as it's a symlink to libSystem.dylib
 OMPI_CHECK_FUNC_LIB([ceil], [m])
 
-AC_CHECK_FUNCS([asprintf snprintf vasprintf vsnprintf openpty isatty getpwuid fork waitpid execve pipe ptsname setsid mmap tcgetpgrp posix_memalign strsignal sysconf syslog vsyslog regcmp regexec regfree _NSGetEnviron socketpair strncpy_s _strdup usleep mkfifo dbopen dbm_open statfs statvfs])
+AC_CHECK_FUNCS([asprintf snprintf vasprintf vsnprintf openpty isatty getpwuid fork waitpid execve pipe ptsname setsid mmap tcgetpgrp posix_memalign strsignal sysconf syslog vsyslog regcmp regexec regfree _NSGetEnviron socketpair strncpy_s _strdup usleep mkfifo dbopen dbm_open statfs statvfs setpgid])
 
 # Sanity check: ensure that we got at least one of statfs or statvfs.
 if test $ac_cv_func_statfs = no -a $ac_cv_func_statvfs = no; then

orte/mca/odls/default/odls_default_module.c

@@ -257,6 +257,7 @@ static int odls_default_kill_local(pid_t pid, int signum)
 {
     pid_t pgrp;
 
+#if HAVE_SETPGID
     pgrp = getpgid(pid);
     if (-1 != pgrp) {
         /* target the lead process of the process
@@ -268,6 +269,7 @@ static int odls_default_kill_local(pid_t pid, int signum)
          */
         pid = pgrp;
     }
+#endif
     if (0 != kill(pid, signum)) {
         if (ESRCH != errno) {
             OPAL_OUTPUT_VERBOSE((2, orte_odls_base_framework.framework_output,
@@ -908,6 +910,9 @@ static int odls_default_fork_local_proc(orte_app_context_t* context,
     
     if (pid == 0) {
 	close(p[0]);
+#if HAVE_SETPGID
+        setpgid(0, 0);
+#endif
         do_child(context, child, environ_copy, jobdat, p[1], opts);
         /* Does not return */
     }