qapi2texi: Include member type in generated documentation

The recent merge of docs/qmp-commands.txt and docs/qmp-events.txt into
the schema lost type information.  Fix this documentation regression.

Example change (qemu-qmp-ref.txt):

  -- Struct: InputKeyEvent

      Keyboard input event.

      Members:
-     'button'
+     'button: InputButton'
           Which button this event is for.
-     'down'
+     'down: boolean'
           True for key-down and false for key-up events.

      Since: 2.0

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1489582656-31133-26-git-send-email-armbru@redhat.com>

scripts/qapi.py

@@ -1105,6 +1105,11 @@ class QAPISchemaType(QAPISchemaEntity):
         }
         return json2qtype.get(self.json_type())
 
+    def doc_type(self):
+        if self.is_implicit():
+            return None
+        return self.name
+
 
 class QAPISchemaBuiltinType(QAPISchemaType):
     def __init__(self, name, json_type, c_type):
@@ -1129,6 +1134,9 @@ class QAPISchemaBuiltinType(QAPISchemaType):
     def json_type(self):
         return self._json_type_name
 
+    def doc_type(self):
+        return self.json_type()
+
     def visit(self, visitor):
         visitor.visit_builtin_type(self.name, self.info, self.json_type())
 
@@ -1188,6 +1196,12 @@ class QAPISchemaArrayType(QAPISchemaType):
     def json_type(self):
         return 'array'
 
+    def doc_type(self):
+        elt_doc_type = self.element_type.doc_type()
+        if not elt_doc_type:
+            return None
+        return 'array of ' + elt_doc_type
+
     def visit(self, visitor):
         visitor.visit_array_type(self.name, self.info, self.element_type)