MacOS X: require SWIG 2.0.12

To fix build of modpython
Add socket traffic stats to listsockets response

Not yet added to Web interface though.
add src/version.cpp to gitignore
Add traffic stats to listsockets webadmin table

Table is not displaying, however. Odd.
Add new columns to listsockets tmpl
Merge pull request #486 from dgw/gitignore-versioncpp

Add version.cpp to .gitignore
Merge commit 'refs/pull/488/head' of github.com:znc/znc