Fix issues with special characters when running mvn

Setting the locale to C will stabilize sed, so it won't stop processing
the mvn output when it encounters invalid characters (like binary data)

This makes it also more viable to add the `alias mvn='mvn-color`, as
the coloring is less obtrusive, and there won't be any issues with sed
breaking because of an invalid character inside the stream
Merge pull request #2242 from sztupy/fix-mvn-color-locale

Fix issues with special characters when running mvn