bug#10823: 24.0.93; Make `C-h d' reporting more consistent and usable

[Jambunathan K <kjambunathan@gmail.com>]

I find that C-h d gives me a fairly good coverage of a particular
"feature" that I am trying to hunt down. Unfortunately for the amount of
information that it prints, the navigation of the *Apropos* buffer is
cumbersome.

Let me explain with an explain. Down below is a snapshot of first few
paragraphs when I do a

  C-h d apropos

Here are a few things that I find noisome. These are documented in the
text below.


----------------
apropos-read-pattern
  Function: Read an apropos pattern, either a word list or a regexp.

<<Big wall of text>>

(fn SUBJECT) 

,---- ^^^^^^^^^^^^^^
| By the time I reach here, I have almost forgotten what "fn" I am looking
| at. I also find this style of reporting inconsisten with C-h v and C-h f
| style of reporting where the function signature is on the top.
`----

----------------

,---- ^^^^^^^^^^^^^^
| Can these separators be converted to page breaks? So that I can move
| between the different blocks using page navigation commands. Doing a
| incremental re-search for -----+ is painful particularly when some of
| the listed commands that have docstring which have horizontal rules in
| them.
`----

apropos
  Command: Show all meaningful Lisp symbols whose names match PATTERN.

<<Another big wall of text>>

(fn PATTERN &optional DO-ALL)

----------------
apropos-command
  Command: Show commands (interactively callable functions) that match
           PATTERN.


,----[ C-h v internal-doc-file-name RET ]
| internal-doc-file-name is a variable defined in `C source code'.
| Its value is "DOC-X"
| 
| Documentation:
| Name of file containing documentation strings of built-in symbols.
| 
| [back]
`----

,----
| Can someone clarify what the file is and what qualifies as "built-in"
| symbols. Does it include the "whole" of what ships with vanilla Emacs or
| just a subset of it. I tried looking around in the info manual. I found
| nothing much which could give me a sense of "coverage" of the reported
| list.
`----