Begin an Intel-specific instruction group.

Add instructions representing Intel's division instructions which use a
numerator that is twice as wide as the denominator and produce both the
quotient and remainder.

Add encodings for the x86_[su]divmodx instructions.

docs/cton_domain.py

@@ -271,7 +271,10 @@ class InstDocumenter(sphinx.ext.autodoc.Documenter):
         return False
 
     def resolve_name(self, modname, parents, path, base):
-        return 'base.instructions', [base]
+        if path:
+            return path.rstrip('.'), [base]
+        else:
+            return 'base.instructions', [base]
 
     def format_signature(self):
         inst = self.object