Document gettext builder and create i18n docs.

doc/builders.rst

@@ -220,6 +220,18 @@ Note that a direct PDF builder using ReportLab is available in `rst2pdf
 
    .. versionadded:: 0.5
 
+.. module:: sphinx.builders.intl
+.. class:: MessageCatalogBuilder
+
+   This builder produces a message catalog file for each reST file or
+   subdirectory.
+
+   See the documentation on :ref:`internationalization <intl>` for further reference.
+
+   Its name is ``gettext``.
+
+   .. versionadded:: 1.XXX
+
 .. module:: sphinx.builders.changes
 .. class:: ChangesBuilder
 

doc/contents.rst

@@ -14,6 +14,7 @@ Sphinx documentation contents
    domains
    builders
    config
+   intl
    theming
    templating
    extensions

doc/intl.rst

@@ -0,0 +1,11 @@
+.. _intl:
+
+Internationalization
+====================
+
+.. versionadded:: 1.XXX
+
+Complementary to translations provided for internal messages such as navigation
+bars Sphinx provides mechanisms facilitating *document* translations in itself.
+It relies on the existing configuration values :confval:`language` and
+:confval:`locale_dirs`.