Also fixes some other S/Mime issues, as described in the bug.
r=ddrinan/ducarroz/darin sr=alecf
git-svn-id: svn://10.0.0.236/trunk@118829 18797224-902f-48f8-a5cc-f745e15eee43
(includes b=115209 Only care for outermost signing/encryption level)
r=javi/ducarroz sr=mscott
git-svn-id: svn://10.0.0.236/trunk@114801 18797224-902f-48f8-a5cc-f745e15eee43