Increase FidoNet echo/area tag max length from 35 to 40/50 chars

Per FMail.txt:
Area name
          This is the name of the conference. It can be up to 50
          characters long. This name is often referred to as the
          area tag.

I did not locate a FidoNet spec to contradict that and support a 35 character maximum area tag length. I think Mystic also has a 50 character area tag limit. So 50 character area tags are fine I guess.

So up to 50 characters are now supported in SBBSecho and SCFG for area tags (for message and file echoes). The exception is the (new to 3.19) optional area tag stored in msgs.cnf/file.cnf is limited to 40 characters due to reserved space limitations. If you need a tag stored per sub (most sysops do not) and it needs to be longer than 40 chars, use the newsgroup name instead (limited to 63 chars).

Changed at the request of Keyop via IRC.