Fix Bug 1087011 - Understand how many www.mozilla.org visitors have DNT enabled
Fix bug 920113, 949163: tags should be from all lang files.

Tags (including "active") should be from all .lang files associated with
a template. So l10n_has_tag() as well as the active state of a page
should include information from all included .lang files from
add_lang_file and set_lang_files calls.

This also moves the check for DEV==True to the helpers, so checking
settings.DEV in templates is no longer necessary.
Restore dev browser release_notes for bug 1088202
Merge pull request #2504 from jgmize/restore-dev-browser-relnotes

Restore dev browser release_notes for bug 1088202
Fix bug 1099433: Add security text and transition document.
Merge pull request #2509 from pmclanahan/add-security-pgp-text-1099433

Fix bug 1099433: Add security text and transition document.
Merge pull request #2427 from kyoshino/bug-1087011-ga-dnt

Fix Bug 1087011 - Understand how many www.mozilla.org visitors have DNT enabled
Merge pull request #2501 from pmclanahan/l10n_has_tag_use_all_lang_files

Fix bug 920113, 949163: tags should be from all lang files.