bug#21231: 25.0.50; doc string of `marker-position'

[Drew Adams]

The doc string is misleading or confusing.  Please follow what is said
in the Elisp manual.

The doc string says:

  Return the position MARKER points at, as a character number.

Character number?  What is that?  It either means nothing or it means
something we don't want to convey here: the integer value of a
character.

The Emacs way of talking about this is to refer to it as a "buffer
position".  It is a positive integer.

The manual just says "position".  If you want to add that it is a
positive integer, fine.

And it would be better if the first line indicated the nil possibility.
Something like:

 Return position of MARKER, or nil if it points nowhere.
 If a position, it is a positive integer.


In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2014-10-20 on LEG570
Bzr revision: 118168 rgm@gnu.org-20141020195941-icp42t8ttcnud09g
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking=yes,glyphs CPPFLAGS=-DGLYPH_DEBUG=1'