Update addr6(1) manual page regarding filter support
Shorten description to fit int 80-characters line
Add missing short-optin
Add support for different encondings of IPv4-embedded addresses
Fix 64-bit encoding of IPv4 addresses
Change encoding names to those of addr6, and fix help information
Fix documentation of --tgt-ipv4 to reflect recent incorporation of different encodings
Change option name such that -f is available for new 'file' option