bug#13923: 24.3.50; doc strings of Isearch commands

[Drew Adams]

The doc strings of `isearch-forward' etc. should describe each of the
arguments.  That includes arg NO-RECURSIVE-EDIT.  This applies to all
Isearch commands.
 
The doc string of `isearch-mode', especially, needs to describe each of
its arguments.  It currently describes none of them.
 
In GNU Emacs 24.3.50.1 (i386-mingw-nt5.1.2600)
 of 2013-03-04 on ODIEONE
Bzr revision: 111935 yamaoka@jpl.org-20130304102733-4qy111z41qwoh2as
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -IC:/Devel/emacs/build/include --ldflags -LC:/Devel/emacs/build/lib'