Fix a typo.
Note that node Names are case sensitive.
Note that tincctl import is only meant to work with data from tincctl export.
Mention that the -L, -R and -U options are not supported on all platforms.
Don't complain about garbage if we skipped importing a host file.
Better error messages when using -L, -R or -U on platforms that do not support it.
Always complain if too many arguments are given for tincctl commands.
Check HMAC before sequence number.