Better error/warning messages for common problems

[cayhorstmann]

1. Can/should one give a warning for #EDIT instead of ##EDIT?
2. If the name of the file equals the name of the function, ##CALL doesn't work. (Esoteric Python-only problem)
3. A //HIDE, not in the first line, without a matching //EDIT yields "No solution file". A //HIDE in the miiddle of the file should not be taken as a non-solution file. It could hide everything from that point or give an error.