SecretAgent can modify or delete the HTTP User-Agent header before
it's sent to web servers.  User-Agent is used by web browsers to
inform web servers what browser is being used, browser version,
operating system, and other platform information.  Example:

    Mozilla/4.0 (compatible; MSIE 4.01; MSN 2.5; Windows 95)

Typically "Mozilla" is the code name for "Netscape" and is used to
inform web server applications that certain features such as HTML
tables are supported.  However, the above browser is Microsoft
Internet Explorer 4.01, not Netscape.  MSIE masquerades as Mozilla to
ensure User-Agent driven web server applications enable Netscape
enhanced features which MSIE also supports.

Also notice that the above User-Agent includes the Microsoft Network
Version and operating system version.

SecretAgent is meant to be used by people that don't want to play
User-Agent games or disclose certain platform information to the
world.  I usually set my User-Agent to "Muffin (muffin.doit.org)".

This filter has the following configurable preferences:

* SecretAgent.userAgent

  User-Agent value to send.  A value of NONE will cause the User-Agent
  header to be removed.
