[PATCH] Clean up 'make help' output for documentation targets.

Here's a patch that cleans up the "make help" output a bit for the
documentation targets.

Currently the documentation targets are listed completely different than
all the other targets :

  Documentation targets:
    Linux kernel internal documentation in different formats:
    xmldocs (XML DocBook), psdocs (Postscript), pdfdocs (PDF)
    htmldocs (HTML), mandocs (man pages, use installmandocs to install)

with this patch they are more in line with the rest of the output :

  Documentation targets:
   Linux kernel internal documentation in different formats:
    htmldocs        - HTML
    installmandocs  - install man pages generated by mandocs
    mandocs         - man pages
    pdfdocs         - PDF
    psdocs          - Postscript
    xmldocs         - XML DocBook

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>