Import libtelnet @ https://github.com/seanmiddleditch/libtelnet
Extract telnet releated stuff to net/telnet.cc

Aslo extract outbuf to a seperate module.
Fix debugmalloc.
Add gitignore for sources
Add missing m4 libraries.
Update travis build script.
Update makefile for libtelnet.
Add a comment about -march/-mtune
Fix compiling error for libtelnet
Add -j 4 for travis build.
Merge pull request #181 from sunyc/master

Replaced in-house TELNET implementation with libtelnet