Replacement with regexes!

Replace regexes by default, like grep, and like other replacement tools.

To treat patterns as text literals (the old behaviour), use the --literal/-l option.

The --escape/-e option is deprecated: it has an illogical name, since it unescapes the pattern, and it has little use (grep has no equivalent).

The formatting of the man page is fixed: no more paragraph break in the middle of the synopsis.

Feedback on this release is most welcome, both on the design and about any bugs I may have introduced.