Improved topological map showing program,reduced code duplication.
The result was my expectation,but was not the best.It's necessary to
develop a new algorithm.
Expanded the discovery scope,form 128.1 to 191.255,instead of from
182.1 to 191.255.Lots more devices were discovered,including some of
windows and aix servers.
Moreover,some of strange devices were discovered too,whose SYSOID is
1.3.6.1.4.1.6889.1.69.1.6,SYSDESCR is VxWorks SNMPv1/v2c Agent by
Wind River Systems.