Log Message:
swirc: update to 3.3.7.

## [3.3.7] - 2022-10-22 ##
- **Added** code to the following scripts:
  - `posixshell/link_with_gnu_libidn.sh`
  - `posixshell/link_with_libnotify.sh`
- **Added** preprogrammed IRC network [OFTC](https://www.oftc.net/)
- **Added** usage of `swircpaths.h`, a header which is automatically
  generated during the build process.
- **Fixed** a case of a possibly negative array subscript