[Markdown] Add proper "white-space" handling for Markdown rendering

[MasterInQuestion]

	Specifically, make proper interpretation of forms like:
[[
<pre style="white-space: pre-wrap; word-wrap: break-word; tab-size: 4">
...
</pre>
]]
	.
	Precisely, this is not an issue specifically bound to "white-space" nor "<pre>", but the general parsing of HTML-like elements.
	Currently the implementation seems to outright ignore "style" attributes. (not thoroughly verified)