Doc strings within 80 char limit for hmouse-tag.el

[matsl]

What

Doc strings within 80 char limit for hmouse-tag.el.

Why

Warnings, warnings, warnings...

[matsl]

@rswgnu Had to mix committing changes in the GUI with rebase and resolve some more complicated changes manually.

When there are multi line changes I think it will be easier for me if all lines in the docstrings are changed within one suggested commit. I think that is possible by selecting multiple lines when creating the suggestion. Mark the fist line and use the mouse to drag to the last line you want to change.