Add missing letter.odt in package

issue3864
(grafted from f506ee0dda9b8a3c7a439f5165285cf8d23ab28a)

--HG--
branch : 3.2
extra : source : f506ee0dda9b8a3c7a439f5165285cf8d23ab28a
Prepare release 3.2.1

--HG--
branch : 3.2
Added tag 3.2.1 for changeset 7f44b83406e3

--HG--
branch : 3.2
Increase version number

--HG--
branch : 3.2