[vile] writing an empty file with nonewline

[Brendan O'Dea]

There seems to be a problem when writing out an empty file when
nonewline is set (see http://bugs.debian.org/368007).

 $ vi new-file
 :setl nonewline
 :wq
 [writing...]

Resulting in a file full of newlines.  Note you'll probably want to kill
the process.

The problem appears to be in file.c:actually_write(), where the first
iteration of:

    while ((rp->r_size + offset) >= line_length(lp)) {

has rp->r_size as -1, but since r_size is unsigned the test succeeds and
will do so until decrementing r_size in the body wraps unsigned long.

Not sure exactly where the root of the problem lies; setup_file_region()
seems to copy that -1 value from bp->b_bytecount, which should similarly
be unsigned.

--bod