Fix for warning - undefined property document.charset (bug 253787). Patch by gautheri@noos.fr, r+sr=me, a=asa.

mail/base/content/nsContextMenu.js

@@ -602,7 +602,7 @@ nsContextMenu.prototype = {
       var docshell = document.getElementById( "content" ).webNavigation;
       BookmarksUtils.addBookmark( docshell.currentURI.spec,
                                   docshell.document.title,
-                                  docshell.document.charset,
+                                  docshell.document.characterSet,
                                   false );
     },
     addBookmarkForFrame : function() {
@@ -613,7 +613,7 @@ nsContextMenu.prototype = {
         title = uri;
       BookmarksUtils.addBookmark( uri,
                                   title,
-                                  doc.charset,
+                                  doc.characterSet,
                                   false );
     },
     // Open Metadata window for node