Bug 766606 - [mozilla.org] Firefox download button doesn't block new unsupported operating systems

* Copied the old platform detection code from download.js
* Added Windows 2000 (NT 5.0 and 5.0.1) detection
* Added Windows XP SP1 detection
Bug 900493 update home page redirect to allow its localization
Bug 873087 - Generalized lang file tags

Support for lines like '## tag ##' in lang files, where tag can be any string.
For efficiency, tag lines must be the first lines in the file.
Merge pull request #1126 from dpoirier/bug-873087-lang-file-tags

Bug 873087 - Generalized lang file tags
Bug 826323 - Don't HTML-escape the text in contribute emails
Bug 705416 - Port Firefox Release Notes index page to Bedrock and automate the update
Bug 868178 - Make L10N translator comment tag case-insensitive

* Update playdoh-lib to version that has that change in tower
* Fix one tower import due to a method having been moved
Merge pull request #1114 from dpoirier/bug-826323-dont-encode-contribute-emails

Bug 826323 - Don't HTML-escape the text in contribute emails
Merge pull request #1131 from dpoirier/bug-868178-case-insensitive-l10n-comments

Bug 868178 - Make L10N translator comment tag case-insensitive
Merge pull request #968 from kyoshino/bug-705416-relnotes-index

Bug 705416 - Port Firefox Release Notes index page to Bedrock and automate the update
Merge pull request #1125 from pascalchevrel/Bug-900493-homepage_redirect_update_l10n

Bug 900493 update home page redirect to allow its localization
Merge pull request #975 from kyoshino/bug-766606-unsupported-os

Bug 766606 - [mozilla.org] Firefox download button doesn't block new unsupported operating systems