Added support for 'linelength' setting in CPPLINT.cfg

It is now possible to override the line length per project
by usign 'linelength' setting in CPPLINT.cfg.

R=erg@google.com

Review URL: https://codereview.appspot.com/132050043

git-svn-id: http://google-styleguide.googlecode.com/svn/trunk@137 955884f1-7149-0410-9467-59e7ac3f4d80