bug#42322: 26.3; doc string of `cl-defmethod'

[Drew Adams]

C-h f cl-defmethod:

 (cl-defmethod NAME [QUALIFIER] ARGS &rest [DOCSTRING] BODY)

 Define a new method for generic function NAME.
 I.e. it defines the implementation of NAME to use for invocations where the
 values of the dispatch arguments match the specified TYPEs.
 The dispatch arguments have to be among the mandatory arguments, and
 all methods of NAME have to use the same set of arguments for dispatch.
 Each dispatch argument and TYPE are specified in ARGS where the corresponding
 formal argument appears as (VAR TYPE) rather than just VAR.

Please say that by "dispatch arguments" you mean ARGS.
Please say what the form of ARGS is, as the way to introduce TYPE.

Currently, TYPE appears before any description of what it stands for and
where it occurs (in fact, there is no such clear description of it).

In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor `Microsoft Corp.', version 10.0.18362
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''