Make image/vnd.microsoft.icon be an alias for image/x-icon mime type.

The mime type .ico files is detected as image/vnd.microsoft.icon on some PHP
installations. This fixes the issue by aliasing it to image/x-icon.

Bug: 69437
Change-Id: I1fdb4c7058546d6cdd47b1961706ef84a05dd360
Mark ParserOutput of MessageContent as varying by userlanguage

Hopefully this will stop cache pollution when a MessageContent
ends up in parser cache. MessageContent objects just do
wfMessage()->parse(), which uses user language.

Bug: 41065
Change-Id: I75e8256a61b828cb9fc93227eb517a34ac6b9d15
Merge "Make image/vnd.microsoft.icon be an alias for image/x-icon mime type."
Merge "Mark ParserOutput of MessageContent as varying by userlanguage"