Why is a separate field then needed? Dunno, but probably because the type and
values fields make up an encoded NSSCMSAttribute. (The comment in <nss/cmst.h>
says so, but it took a while before I realized what it meant.) The typeTag and
encoded fields are for NSS internal use or something.

Now Adobe Reader says "The signature includes an embedded timestamp but it is
invalid". Progress...

Change-Id: I390947db8d414a7ceecc1f67aaeed5fa0f66fe6f