pkg_pretend sample used deprecated error message format

Since linux-info.eclass's revision 1.35, which fixed bug #113142, ERROR_* is the preferred format for error message variable names.
Merge pull request #6 from Whissi/master

pkg_pretend sample used deprecated error message format
add info about hardblockers wrt #407597
add info to slot deps wrt #407597
appendices/editor-configuration/emacs: Use <c> tags where appropriate.

Bug 477046.
appendices/editor-configuration/emacs: Update weblinks.

Bug 477046.
appendices/editor-configuration/emacs: Delete outdated information.

Bug 477046.
Merge branch 'master' of github.com:gentoo/devmanual.gentoo.org