The readfile function reads filename and copies it to stdout. No translation
of NEWLINE is done. It keeps track of the longest line it reads and if there
is a subsequent call to longline, the length of that
line, including the NEWLINE character, is returned.
The longline function returns the length, including
the NEWLINE character, of the longest line in filename.
If filename is not specified, it uses the file
named in the last call to readfile.
More than one descriptor can call readfile in the
same frame definition file. In text frames, if one of those calls is made
from the text descriptor, then a subsequent use of longline will always get the longest line of the file read by
the readfile associated with the text
descriptor, even if it was not the most recent use of readfile.