net-im/sshout: fix optimization compiling option and update optional dependency

This update fixes the followings:

• The current upstream Makefile appends '-O1' to CFLAGS, which would inadvertently override any previous optimization option that passed by the user.
• www/elinks has recently been updated to a supported version add optional dependency to it, and remove the related note in 'pkg-message'.

PR: 263391