Reflect all recent changes in the manpage:
- add adhoc-demo and hostap into list of supported modes;
add few examples for them;
- mention encryption/decryption offload for CCMP cipher;
- extend list of driver messages in the DIAGNOSTICS;
- document hostap mode limitations / powersave instability
in the CAVEATS section.
Differential Revision: https://reviews.freebsd.org/D5149