Bug#996085: mrtg: Wrong manpage level: mrtglib.1

[Joao Eriberto Mota Filho]

Package: mrtg
Version: 2.17.7-3
Severity: normal
Tags: upstream

Control: forwarded https://github.com/oetiker/mrtg/pull/48

Considering that mrtglib is a Perl Module, the right level for this
manpage is 3.

Eriberto