a given keyring is registered twice.
* keydb.h, keydb.c (keydb_add_resource): Use flags to indicate a default
keyring. (keydb_locate_writable): Prefer the default keyring if possible.
* g10.c (main): Add --default-keyring option.
section for random gatherers.
* keyring.c (create_tmp_file, rename_tmp_file): Create tmp files with
user-only permissions, but restore the original permissions if the user
has something special set.
* openfile.c (copy_options_file): Create new options file (gpg.conf) with
user-only permissions.
* keydb.c (keydb_add_resource): Create new keyrings with user-only
permissions.
