userspace: add 'rvlan-status' script

This simply sends SIGUSR1 to radiusvlan and sorts the output file.

Example:

wri2 (001bc5090845 <-> 001bc509007d): state configured, vlan 4094, pid 0, fd -1
wri3 (001bc5090846 <-> 00e04c1bfd8d): state configured, vlan 31, pid 0, fd -1
wri4 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri5 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri6 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri7 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri8 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri9 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri10 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri11 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri12 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri13 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri14 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri15 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri16 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri17 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
wri18 (000000000000 <-> ): state down, vlan 0, pid 0, fd -1
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>