Implement EnableDocumentation and friends as setting booleans

Instead of being redefined by (En|Dis)able(Docu|Imple)mentation,
the documentation and implementation environments check the value
of some booleans to know whether to call \comment ... \endcomment
or their normal code (which itself is pretty simple).


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5327 de43f980-851b-0410-b2f7-c40aca1f87e0
Typo: doubled macro parameter characters in a previous commit


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5328 de43f980-851b-0410-b2f7-c40aca1f87e0