Detect -, +, * as bullet points in lists.

- Note that in order to use * as bullet point I had to remove
  the C-style comments part from the default `comments' string.

- In C files, only bulleted list starting with - or + will be
  recognized.

- Add an autogroup setting formatoptions=tcroq in git commit
  message files (.git/COMMIT_EDITMSG).
Always start with a textwidth of 64 characters.