This squashes the following commits from master:

 gpg4libre: import PGP encryption manifest
 Change-Id: Iadd7f8f1194299cb50907d8594114c89c668ebd0

 gpg4libre: open encrypted files also via gpg
 Change-Id: I1f626143e6c8443b4ad0c4fc5bdbd5ab8d56a451

 tdf#114550 use 32 bit random session key for gpg encryption
 Change-Id: I7303be71fd855aa454d07fcae04d7f42e3c9cd9c

 tdf#114550 recognize sym key & init vec as valid f/ decrypt
 Change-Id: Ie366f086a3c14d6b54b91b4edee8cfef1a42c44b

 tdf#114550 don't use PBKDF2 in package for gpg encryption
 Change-Id: Ic96b2193f8541bbd109795fb9c0212a0a10c7344

 gpg4libre: add initial unit test for encryption
 Change-Id: Id782dd865878ae7b8a60c7c80821b1370f6ac7e7

Change-Id: Id77b67a275bf91614ab62b65fdc69e4872247ffc
Reviewed-on: https://gerrit.libreoffice.org/47784Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>