Revert "Remove some previously buggy but dead code that I mistakenly resurrected"

This reverts commit 090f027de1.

proc.cpp

@@ -646,6 +646,11 @@ void job_handle_signal(int signal, siginfo_t *info, void *con)
     /* This is the only place that this generation count is modified. It's OK if it overflows. */
     s_sigchld_generation_count += 1;
     got_signal = 1;
+
+    /* pca: I can't justify this kill() call */
+    int errno_old = errno;
+    kill(0, SIGIO);
+    errno=errno_old;
 }
 
 /**