Fixed #7318 -- Cleaned up the template inheritance logic, specifically to...

    def render(self, context):

        compiled_parent = self.get_parent(context)

        pos = 0

        while isinstance(compiled_parent.nodelist[pos], TextNode):

            pos += 1

        parent_is_child = isinstance(compiled_parent.nodelist[pos], ExtendsNode)

        parent_blocks = dict([(n.name, n) for n in compiled_parent.nodelist.get_nodes_by_type(BlockNode)])

        for block_node in self.nodelist.get_nodes_by_type(BlockNode):

            # Check for a BlockNode with this node's name, and replace it if found.

                # parent block might be defined in the parent's *parent*, so we

                # add this BlockNode to the parent's ExtendsNode nodelist, so

                # it'll be checked when the parent node's render() is called.

                if parent_is_child:

                    compiled_parent.nodelist[pos].nodelist.append(block_node)

                # Find out if the parent template has a parent itself

                for node in compiled_parent.nodelist:

                    if not isinstance(node, TextNode):

                        # If the first non-text node is an extends, handle it.

                        if isinstance(node, ExtendsNode):

                            node.nodelist.append(block_node)

                        # Extends must be the first non-text node, so once you find

                        # the first non-text node you can stop looking. 

                        break

            else:

                # Keep any existing parents and add a new one. Used by BlockNode.

                parent_block.parent = block_node.parent

            # Inheritance from local context with variable parent template

            'inheritance25': ("{% extends context_template.1 %}{% block first %}2{% endblock %}{% block second %}4{% endblock %}", {'context_template': [template.Template("Wrong"), template.Template("1{% block first %}_{% endblock %}3{% block second %}_{% endblock %}")]}, '1234'),

            # Set up a base template to extend

         	'inheritance26': ("no tags", {}, 'no tags'),

         	# Inheritance from a template that doesn't have any blocks

         	'inheritance27': ("{% extends 'inheritance26' %}", {}, 'no tags'),

            ### I18N ##################################################################

            # {% spaceless %} tag