When we don't set edittop in read_line(), we don't need to readjust it in
read_file(), because in that particular case it will still be pointing at
current.  And since fileptr is a new, freshly created line, it can never
be equal to filebot, so there is no point in comparing them.

If more than one line was inserted at the beginning of the file, leave it
up to the screen handling to set edittop to what it should be.

Move the setting of fileage a bit down, to its sister setting: the line
at current gets "connected" either to the top-of-file pointer or to the
last line of the inserted file.