That way, unrecognized versions of Alt-Ergo (e.g. 2.0) are no longer
associated to obsolete versions, by default.

If drivers in why3.conf are simple names like "alt_ergo", then the driver file
is search as <datadir>/drivers/alt_ergo.drv

This behavior is now the same as when a driver is given with option -D on the
command line for why3prove, why3replay or why3extract

Reminder: the datadir is either given as
1) the environment variable WHY3DATA
2) the field "datadir" of the [main] section of the
   why3 config file if exists
3) or by default the compile-time datadir

To install the Why3-related Vim files, just create a symbolic link:
  ln -s "$(why3 --print-datadir)/vim" ~/.vim/bundle/why3

Thanks to Johanness Kanig for the suggestion.

Use an optional 'words argument to regexp-opt instead of explicitly
surrounding the result with special chars.