Fix a hard-to-find bugaboo in the struct file list sysctl. The code was

Fix a hard-to-find bugaboo in the struct file list sysctl.  The code was
not properly calculating the required buffer size because it was ignoring
the fact that descriptor tables are shared between threaded processes.  Simply
adding fp->f_count for the fp's in the filehead list doesn't do the job if
a system is running threaded processes.

Reported-by: "Erik P. Skaalerud" <erik@pentadon.com>