bug#21704: 25.0.50; Package (package.el) doc should mention effects on `load-path'

[Drew Adams <drew.adams@oracle.com>]

Apparently (at least from searching package.el and (emacs) `Packages'
and its subnodes), nowhere do we tell users the effect of using the
package system on `load-path'.  (Variable `load-path' is mentioned in a
couple of doc strings, but only for "internal-only" functions.)

There is this comment in the Commentary of `package.el':

;; At activation time we will set up the load-path and the info path,
;; and we will load the package's autoloads.  If a package's
;; dependencies are not available, we will not activate that package.

I think it is important (helpful) to explicitly make the connection for
users between `load-path' and the package system.  Please consider
making it clear.  Even just a statement such as the one in that comment
would help.

Here is one demonstration of the confusion that might be avoided if such
information were made more readily available:

http://lists.gnu.org/archive/html/help-gnu-emacs/2015-10/msg00331.html

In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2015-10-06
Bzr revision: a4a98a1b2568793ead43e824ecf227768759df12
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''