ff tools upgrade to support FreeBSD 13.0.

Add tool: netstat.

Including libraries: libutil,libmemstat,libxo.

Add tool: ifconfig.

Changes:
Remove directory `ipc`, and add a new directory `compat`.
Directory `compat` includes some FreeBSD source files to be compatible
with Linux.
Port Fre

Add tool: ifconfig.

Changes:
Remove directory `ipc`, and add a new directory `compat`.
Directory `compat` includes some FreeBSD source files to be compatible
with Linux.
Port FreeBSD ifconfig to F-Stack.

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