Warn if lines have a blank at the end of line

This was changed in ee8cc207, now that we have fixed the formatting
in the VTK source files we should warn at commit time if there are
trailing white spaces.

Change-Id: Id7e2a6b0a0aad57cba5809cee60c50bdff833fb7
Merge topic 'warn-for-trailing-space' into master

1a9e9eab Warn if lines have a blank at the end of line