Release procedure:

* Update main doc/latex/biblatex/RELEASE file
* Make sure doc has up to date release information at end
* Change biblatex.sty \blx@bcfversion if controlfile format is changed.
  This is not done by build script automatically as the package version could change without
  the interface version changing. Don't forget that changing this needs matching change in Biber
  otherwise Biber will report a .bcf version mismatch.
* Change biblatex.sty \blx@bblversion if bbl format is changed.
  This is not done by build script automatically as the package version could change without
  the interface version changing. Don't forget that changing this needs matching change in Biber
  otherwise biblatex will report a .bbl version mismatch.
* Tag with release tag
* Run build.sh in root dir to create release files.
