Upgrade to Sphinx 1.5.3

Read the Docs is now using the latest version of Sphinx, so upgrade our
recommended version too.

As of Sphinx 1.4, index entries are 5-tuples instead of 4-tuples. Update
the Cretonne Sphinx domain to generate the new 5-tuples.

Since we're over this compatibility bump, there's no reason to recommend
a specific Sphinx version, so just go back to 'current'.

README.rst

@@ -65,11 +65,10 @@ Building the documentation
 To build the Cretonne documentation, you need the `Sphinx documentation
 generator <http://www.sphinx-doc.org/>`_::
 
-    $ pip install sphinx==1.3.5 sphinx-autobuild
+    $ pip install sphinx>=1.4 sphinx-autobuild sphinx_rtd_theme
     $ cd cretonne/docs
     $ make html
     $ open _build/html/index.html
 
-The specific Sphinx version is currently used by Read the Docs. Sphinx 1.4 has
-been released, but produces lots of warnings about four-column indices. We'll
-upgrade when Read the Docs does.
+We don't support Sphinx versions before 1.4 since the format of index tuples
+has changed.

docs/cton_domain.py

@@ -65,7 +65,8 @@ class CtonObject(ObjectDescription):
         indextext = self.get_index_text(name)
         if indextext:
             self.indexnode['entries'].append(('single', indextext,
-                                              targetname, ''))
+                                              targetname, '', None))
+
 
 # Type variables are indicated as %T.
 typevar = re.compile('(\%[A-Z])')
@@ -113,6 +114,7 @@ class CtonType(CtonObject):
     def get_index_text(self, name):
         return name + ' (IL type)'
 
+
 sep_equal = re.compile('\s*=\s*')
 sep_comma = re.compile('\s*,\s*')