[1.9.x] Added some function links in translation docs

Backport of 9a6fc96 from master.

docs/ref/utils.txt

@@ -1128,6 +1128,12 @@ For a complete discussion on the usage of the following see the
 
         ``override`` is now usable as a function decorator.
 
+.. function:: check_for_language(lang_code)
+
+    Checks whether there is a global language file for the given language
+    code (e.g. 'fr', 'pt_BR'). This is used to decide whether a user-provided
+    language is available.
+
 .. function:: get_language()
 
     Returns the currently selected language code. Returns ``None`` if

docs/topics/i18n/translation.txt

@@ -1888,14 +1888,15 @@ For example::
 Calling this function with the value 'de' will give you ``"Willkommen"``,
 regardless of :setting:`LANGUAGE_CODE` and language set by middleware.
 
-Functions of particular interest are ``django.utils.translation.get_language()``
-which returns the language used in the current thread,
-``django.utils.translation.activate()`` which activates a translation catalog
-for the current thread, and ``django.utils.translation.check_for_language()``
+Functions of particular interest are
+:func:`django.utils.translation.get_language()` which returns the language used
+in the current thread, :func:`django.utils.translation.activate()` which
+activates a translation catalog for the current thread, and
+:func:`django.utils.translation.check_for_language()`
 which checks if the given language is supported by Django.
 
 To help write more concise code, there is also a context manager
-``django.utils.translation.override()`` that stores the current language on
+:func:`django.utils.translation.override()` that stores the current language on
 enter and restores it on exit. With it, the above example becomes::
 
     from django.utils import translation