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

[Drew Adams]

> > Do you have a suggestion as to where in the manual we should mention the
> > load-path impact?
> 
> How about in Package Installation? (see attached patch)

The location might be OK, but I don't see how that text responds to the
bug report.  I don't see how it "tell[s] users the effect of using the
package system on `load-path'."  It doesn't "mention what using the
package system has as effects [on `load-path']."  It doesn't even
mention variable `load-path'.  Does it have no effect on `load-path'?
Does it alter `load-path' (how)?