#3 Improve "const correctness"

[Markus Elfring]

Would you like to apply the advices from the article
"http://en.wikipedia.org/wiki/Const_correctness" to
your sources?
I suggest to add the key word "const" to the type
specifiers for parameters like the following.
- r (function "print_request")

http://cvs.sourceforge.net/viewcvs.py/vmps/vmpsd/vqp.h?rev=1.1.1.1&view=markup

- host, community, port, speed, duplex (function
"set_port_speed")

http://cvs.sourceforge.net/viewcvs.py/vmps/vmpsd/snmp.h?rev=1.1.1.1&view=markup