Reflow Python license comment blocks to 72 characters

PEP-8 dictates that ‘For flowing long blocks of text with fewer
structural restrictions (docstrings or comments), the line length should
be limited to 72 characters.’  In commit 9efa55e, I forgot to do this
and wrapped all the license comment blocks at 79 characters instead.
This commit reflows the license text to fit within the prescribed
72-character width.