HTML API: revise order of elements in HEAD section

The HTML specification [1] does not specify a strict order for the
elements within the HEAD section, other than Content-Type appearing
within the first 1024 bytes of the document.

Microsoft / Internet Explorer has stricter guidelines when it comes to
defining compatibility mode [2]: "The X-UA-Compatible header [...] must
appear in the header of the webpage (the HEAD section) before all other
elements except for the title element and other meta elements."

This commit reorganizes html_page_top1() function to:

• define Content-Type as the HEAD's first element
• allow users to set X-UA-Compatible in $g_meta_include_file
• include CSS after defining the TITLE, together with other LINK tags

Fixes 0017176

[1] http://www.w3.org/TR/html5/document-metadata.html
[2] http://msdn.microsoft.com/en-us/library/jj676915%28v=vs.85%29.aspx