Bugfix: make longer telnet cmdfunc names
The maximum number of cmdfunc names is 20, which IMO is too low. Worse, if it's
longer, nothing will warn us because C will just fill the array to it's end
(without \0 at the end). To remedy this:
- Allow longer names till 64 bytes (I hit the previous limit of 20)
- Check that the name is within the length limit: if somebody wants a very long
name, the strnlen() will return the maximum length, hitting that assertion.
- When reading a command during runtime, allow the corresponding maximum length.
On that occasion, also increase total number of permitted cmdfuncs.