[Rd] documentation enhancement: Note in ?seek for Windows (PR#7943)

[tplate@blackmesacapital.com]

[I started a new bug report for this issue because it was not the 
primary issue in the original discussion, which was PR#7899]

ligges at statistik.uni-dortmund.de wrote:
 > Tony Plate wrote:
 > [snip]
 >>ligges at statistik.uni-dortmund.de wrote:
 >>[snip]
 >>>Note that ?seek currently tells us "The value returned by
 >>>seek(where=NA) appears to be unreliable on Windows systems, at least
 >>>for text files."
 >>>It would be nice if this comment could be removed, of course ....
 >>
 >>
 >>May the explanation could be given that this happens with text files
 >>because Windows inserts extra characters at end-of-lines when reading
 >>"text" mode files (but with binary files, things should be fine.) This
 >>particular issue is documented in Microsoft Windows documentation (e.g.,
 >>at http://msdn2.microsoft.com/library/75yw9bf3(en-us,vs.80).aspx, found
 >>by searching on Google using the terms "fseek windows documentation").
 >>Are there any known issues using seek with binary files under Windows?
 >>If there are not, then the caveat could be made specific to text files
 >>and all vagueness removed.
 >
 >
 > Hmm, all I find (including your link) is Windows CE related ...
 >
 > Uwe Ligges

For the record, the documentation I pointed to is for Windows 2000 etc, 
and is not just related to Windows CE (Uwe retracted that claim in a 
private email).

So, the suggestion to refine the note in ?seek stands.  Perhaps 
src/library/base/man/seek.Rd could be changed as follows:

OLD:

#ifdef windows
   The value returned by \code{seek(where=NA)} appears to be unreliable
   on Windows systems, at least for text files.  Clipboard connections
   can seek too.
#endif

NEW:

#ifdef windows
   The value returned by \code{seek()} is unreliable
   on Windows systems for text files.  This is because the Windows
   file-I/O functions can insert extra characters at end-of-lines
   when working with text mode files.  Binary mode files should not
   be affected by this issue.  Clipboard connections can seek too.
#endif

Of course, if someone knows that the return value of seek() is 
unreliable on Windows for binary files, this documentation change is 
innappropriate (and then the documentation should probably be changed 
from "appears to be unreliable, at least for text files" to "is 
unreliable, for both binary and text files".

-- Tony Plate