inetd.8: Sort options

While here:

• Cluster flags without arguments together.
• Simplify the synopsis of the -a flag. There is no need to distinguish between address and hostname there.
• Add a missing argument to the -a flag in the description section.
• Fix some typos.

MFC after: 3 days

(cherry picked from commit 593ad024e4ed04e4c875446e5277d82e3111848f)