Update to 3.12.1:

3.12.1
======
* yelp-check: Return non-zero exit status when there are broken hrefs

3.12.0
======
* Stable release. No changes since 3.11.5

3.11.5
======
* yelp-build: Added -i option to ignore missing media files
* yelp-build: Added -p option to provide path for external files
* yelp-build: Set LC_ALL instead of LANG for awk, #709354
* yelp-check: Added check for missing media files
* yelp-check: Added tool to check Mallard page licenses
* yelp.m4: Use AS_HELP_STRING instead of AC_HELP_STRING, #709657

3.11.3
======
* yelp.m4: no-lc-dist option to disable disting the generated lc files (Christian Persch)

3.11.2
======
* yelp.m4: Added no-lc-media-links option for YELP_HELP_INIT
* yelp.m4: Reverted HELP_MEDIA_NODUP and YELP_INIT_HELP

3.11.1
======
* yelp-build: Handle conditional processing and other logic when copying
  media and other external files, #709951
* yelp-check: Support validate on DocBook 5 documents
* yelp-check: Support explicitly allowed namespaces in strict validation
* yelp-check: Fixed POSIX shell syntax error, #710331 (Michael Biebl)
* yelp-new: Now much smarter about output file paths and extensions
* yelp.m4: Added HELP_MEDIA_NODUP to install media without locale symlinks
* yelp.m4: Added YELP_INIT_HELP as version-checking replacement for
  YELP_HELP_INIT

3.10.0
======
* Stable release. No changes since 3.9.90

3.9.90
======
* yelp-build: Fix directionality issues for Mallard
* yelp-check: Allow xml: attributes when validating in strict mode

3.9.1
=====
* Fixed BSD compatibility issue in calling mktemp
* Fixed 'make pot' when srcdir != builddir (Michael Terry)
* yelp-check validate: Validate cache files
* yelp-check ids: New command to check Mallard page IDs
* yelp-build epub: Fixed issue with directory for media

3.6.1
=====
* yelp-check: Added 'links -i' to ignore xrefs with hrefs
* yelp-check: Fixed extra angle brack in 'comments'
fmt