Merge pull request #177 from stweil/1.10.x

Typo fixes and text cleanups in comments
Fix GPL text (FSF address was wrong)

The address of the FSF changed many years ago. Instead of using the
current address, the new text was copied from GPL 3 which simply
redirects to a URL. This avoids unnecessary future changes when the
FSF moves again.

Signed-off-by: Stefan Weil <sw@weilnetz.de>