Added a --linelength flag so that the default of 80 can be changed.

Review URL: https://codereview.appspot.com/22180043

Patch from Matt Clarkson <mattyclarkson@gmail.com>.

git-svn-id: http://google-styleguide.googlecode.com/svn@117 955884f1-7149-0410-9467-59e7ac3f4d80
A false positive occurs when a user specifies a using declaration for a stream operator:

    10: using ns::operator<<;
    file.cpp:10: Missing spaces around << [whitespace/operators] [3]

The regular expression has been updated to find this valid use case of the <<
text string.

Review URL: https://codereview.appspot.com/22190043

Patch from Matt Clarkson <mattyclarkson@gmail.com>.

git-svn-id: http://google-styleguide.googlecode.com/svn@118 955884f1-7149-0410-9467-59e7ac3f4d80