coding style: reduce text width to 109 characters

coding style: reduce text width to 109 characters

Patches are shown on github with a fixed width (no matter how wide the window
is). When line numbers are high (we have some files with 5 digit line numbers),
the diff does not fit, and horizontal scrolling must be used when viewing the
patch. This is super annoying. Let's reduce the width a bit. I think 109 is
still very wide, but at least the github issue should be alleviated.