Extended code blocks should only contain single code tag

[gocom]

Currently Textile's long code block generation is a bit semantically flawed. When the block isn't extended, it will contain single code element, but in extended mode, the code blocks act like paragraphs, when they shouldn't.

The following:

bc.. Hello

World!

Generates:

<pre><code>Hello</code>

<code>World!</code></pre>

While it really should be generating:

<pre><code>Hello

World!</code></pre>

The two-level wrappers Textile uses in block/fBlock, only are applicable to blockquotes. For code blocks both elements should be specified in the outer, rather than line.