The line prefix was not actually indicating what it should indicate.
In particular, anything in a "changed" block would show a "!" even
if the entire line was added or deleted. Better to print nothing than
something that's wrong.

fix a couple of diff issues: shouldn't be any need to html encode before finding diffs; move quantifier outside regex condition

Previously the media manager created an empty namespace whenever you
opened a non-existing namespace with upload permissions. Now the current
namespace is only displayed in the tree but not actually created.

It seems, some servers require a special Status: header for sending the
HTTP status code from PHP (F)CGI to the server. This patch introduces a
new function (adopted from CodeIgniter) for simplifying the status
handling.

There is a condition inside idfilter() function that helps Apache on Windows to properly handle colon as a namespace separator by replacing it with semicolon. However, this is not necessary on Microsoft IIS server so the condition was improved.