bug#28237: 25.2; doc string of `Info-virtual-nodes'

[Drew Adams]

Neither OPERATION nor HANDLER is specified well.

1. These parts of the doc string are incomprehensible:

     OPERATION is one of the following operation symbols `find-node'
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     that define what HANDLER function to call instead of calling the
     default corresponding function to override it.
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

   I can't even parse the first bit.  Is it trying to say that OPERATION
   must be `find-node'?  (No idea.)

   The second bit: what is the "default corresponding function"?  What
   does that mean?  Default wrt what?  Corresponding to what?

2. HANDLER is not specified at all.  No doubt it is a function.  But
   what arguments can or must the function accept?


In GNU Emacs 25.2.1 (x86_64-w64-mingw32)
 of 2017-04-24
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --without-dbus --without-compress-install 'CFLAGS=-O2
 -static -g3''