Fix icon license in COPYING

The css filename moved, so update that. Also, since I1240e45d these
have come from Tango rather than Apache.

Change-Id: Ie0c60be8d1a67a20171dba0374e544c97663d276

Author: dborowitz

COPYING

@@ -422,12 +422,33 @@ lang-xq.js: Copyright (C) 2011 Patrick Wied
    limitations under the License.
 
 
-Apache Icons embedded in main/webapp/+static/gitiles.css
-========================================================
-Public Domain Icons
-
-These icons were originally made for Mosaic for X and have been included in the
-NCSA httpd and Apache server distributions in the past. They are in the public
-domain and may be freely included in any application. The originals were done
-by Kevin Hughes ([email protected]). Andy Polyakov tuned the icon colors and
-added few new images.
+Tango Icons embedded in main/webapp/+static/base.css
+====================================================
+Public Domain Dedication
+
+The person or persons who have associated work with this document (the
+"Dedicator" or "Certifier") hereby either (a) certifies that, to the best of
+his knowledge, the work of authorship identified is in the public domain of the
+country from which the work is published, or (b) hereby dedicates whatever
+copyright the dedicators holds in the work of authorship identified below (the
+"Work") to the public domain. A certifier, moreover, dedicates any copyright
+interest he may have in the associated work, and for these purposes, is
+described as a "dedicator" below.
+
+A certifier has taken reasonable steps to verify the copyright status of this
+work. Certifier recognizes that his good faith efforts may not shield him from
+liability if in fact the work certified is not in the public domain.
+
+Dedicator makes this dedication for the benefit of the public at large and to
+the detriment of the Dedicator's heirs and successors. Dedicator intends this
+dedication to be an overt act of relinquishment in perpetuity of all present
+and future rights under copyright law, whether vested or contingent, in the
+Work. Dedicator understands that such relinquishment of all rights includes the
+relinquishment of all rights to enforce (by lawsuit or otherwise) those
+copyrights in the Work.
+
+Dedicator recognizes that, once placed in the public domain, the Work may be
+freely reproduced, distributed, transmitted, used, modified, built upon, or
+otherwise exploited by anyone for any purpose, commercial or non-commercial,
+and in any way, including by methods that have not yet been invented or
+conceived.