bug#19682: 25.0.50; `other-window' doc string should say that by default it selects win in same frame

[Drew Adams]

The doc string does not describe the default behavior: select another
window in the same frame, if there is one.

The doc string refers to the doc for `next-window', for the reader to
find out what ALL-FRAMES does - even for the default, nil, case.

It is fine to refer to `next-window' for ALL-FRAMES (e.g. for full
understanding and for non-interactive use).  But surely the default
interactive behavior should be described.

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'