bug#18637: 24.4.50; doc of frame parameter DISPLAY vs actual value on MS Windows

[Drew Adams]

In (elisp) `Basic Parameters' I see this description of frame parameter
`display':

  The display on which to open this frame.  It should be a string of
  the form `"HOST:DPY.SCREEN"', just like the `DISPLAY' environment
  variable.

But if I evaluate `(frame-parameters)' on MS Windows I see this value
for parameter `display': "w32".

"w32" does not seem to fit the form `"HOST:DPY.SCREEN"'.  What gives?

And why is that string surrounded by `...'?  And why aren't the
components of that "form" described: What are acceptable values for
HOST, DPY, and SCREEN?

(I assume that the `:' and `.' are to be taken literally here, and that
HOST, DPY, and SCREEN are placeholders, although there is zero
explanation of this.)

Also, I searched the manual case-sensitively for DISPLAY, and found no 
description/specification/explanation of "the `DISPLAY' environment variable.  
So referring users to that env var to find a specification
of the form `"HOST:DPY.SCREEN"' is unhelpful and misleading.

Please clear up this doc - make it properly specify what form the value
of parameter `display' takes.


In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-09-15 on LEG570
Bzr revision: 117884 dancol@dancol.org-20140915050944-sqsajysnwef51f9m
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'