Rename contrib/tools/chkfmt to contrib/tools/chkfmt.sh; refactor:
* Increase the max line length for contrib/**/*.[ch] from 96 to 100.
* Set the max line length for ci_*.sh to 100.
* Use `basename $0` instead of the hard-coded script name.
* Update comments.
Remove contrib/tools/reindent. For automated code formatting, including
indentation, we need a robust solution.
Add an empty line after the hashbang line in all scripts.
Remove the "last changed" version info from comment headers.
(The version control system maintains this information automatically.)
