vim: do not set nocompatible explicitly

As it used to say in the config itself, the presence of .vimrc implies
this setting.
vim: add author notice at the beginning
vim: add spacing to make folds prettier
vim: fix copy-pasted setting for Perl
vim: for git commits, go to the end of the 1st line
vim: with `autocmd`, use `setlocal`, not `set`