debug output: declutter process table

Before:

startup_selftests: dry-running oom kill...
pid     1: badness  -1 VmRSS      -1 uid   -1 oom_score_adj   -1 "systemd"
pid     2: badness   0 VmRSS       0 uid    0 oom_score_adj   -1 "kthreadd"
pid     3: badness   0 VmRSS       0 uid    0 oom_score_adj   -1 "pool_workqueue_release"
pid     4: badness   0 VmRSS       0 uid    0 oom_score_adj   -1 "kworker/R-rcu_g"
pid     5: badness   0 VmRSS       0 uid    0 oom_score_adj   -1 "kworker/R-rcu_p"
pid     6: badness   0 VmRSS       0 uid    0 oom_score_adj   -1 "kworker/R-slub_"

After:

startup_selftests: dry-running oom kill...
  PID OOM_SCORE  RSSkiB  UID OOM_SCORE_ADJ  COMM
    1        -1      -1   -1            -1 "systemd"
    2         0       0    0            -1 "kthreadd"
    3         0       0    0            -1 "pool_workqueue_release"
    4         0       0    0            -1 "kworker/R-rcu_g"
    5         0       0    0            -1 "kworker/R-rcu_p"
    6         0       0    0            -1 "kworker/R-slub_"

kill.c

@@ -403,10 +403,15 @@ void debug_print_procinfo(procinfo_t* cur)
         return;
     }
     fill_informative_fields(cur);
-    debug("pid %5d: badness %3d VmRSS %7lld uid %4d oom_score_adj %4d \"%s\"",
+    debug("%5d %9d %7lld %5d %13d \"%s\"",
         cur->pid, cur->badness, cur->VmRSSkiB, cur->uid, cur->oom_score_adj, cur->name);
 }
 
+void debug_print_procinfo_header()
+{
+    debug("  PID OOM_SCORE  RSSkiB   UID OOM_SCORE_ADJ  COMM\n");
+}
+
 /*
  * Find the process with the largest oom_score or rss(when flag --sort-by-rss is set).
  */
@@ -422,6 +427,8 @@ procinfo_t find_largest_process(const poll_loop_args_t* args)
         clock_gettime(CLOCK_MONOTONIC, &t0);
     }
 
+    debug_print_procinfo_header();
+
     procinfo_t victim = { 0 };
     while (1) {
         errno = 0;