(scan_message): Don't set first elements of fromheader and subjheader to

'\0'; that was pointless.  Don't assign to line[--len], only decrement
len; line is a private buffer beloging to fgetln and we should not be
scribbling in it; this was also pointless anyway.  Set
fromheader[fromcount] to '\0' after copying the characters from line
into it; do the same for subjheader.