Update to 2.1.20.

• gpg: New properties 'expired', 'revoked', and 'disabled' for the import and export filters.
• gpg: New command --quick-set-primary-uid.
• gpg: New compliance field for the --with-colon key listing.
• gpg: Changed the key parser to generalize the processing of local meta data packets.
• gpg: Fixed assertion failure in the TOFU trust model.
• gpg: Fixed exporting of zero length user ID packets.
• scd: Improved support for multiple readers.
• scd: Fixed timeout handling for key generation.
• agent: New option --enable-extended-key-format.
• dirmngr: Do not add a keyserver to a new dirmngr.conf. Dirmngr uses a default keyserver.
• dimngr: Do not treat TLS warning alerts as severe error when building with GNUTLS.
• dirmngr: Actually take /etc/hosts in account.
• wks: Fixed client problems on Windows. Published keys are now set to world-readable.
• tests: Fixed creation of temporary directories.
• A socket directory for a non standard GNUGHOME is now created on the fly under /run/user. Thus "gpgconf --create-socketdir" is now optional. The use of "gpgconf --remove-socketdir" to clean up obsolete socket directories is however recommended to avoid cluttering /run/user with useless directories.
• Fixed build problems on some platforms.