Update dconf to 0.26.0

XXX is SUBST_CLASSES.Darwin+= libname still needed?

Changes in dconf 0.26.0
========================

None.

Changes in dconf 0.25.1
========================

 - the libdbus-1 backend has been removed.  dconf now always uses GDBus.

 - support has been added for system administration frameworks to set up
   the dconf profile via a file placed in the XDG_RUNTIME_DIR or in
   /run/dconf/.  In the case of the file in /run/dconf/, it is not
   possible to modify the proile, even via the DCONF_PROFILE environment
   variable, which makes it slightly more difficult to evade lockdown.

 - directory resets are now implemented properly in DConfChangeset which
   means that reading a subkey through a changeset that contains a reset
   for a parent directory of that key will return TRUE with a NULL value

 - a new API dconf_client_read_full() has been added which allows
   reading the user value, the default value, or querying what the
   effective value would be if a changeset were to be applied.

 - a new API has been added for listing the locks that are in effect:
   dconf_client_list_locks()

 - DConfClient has a new "writability-changed" signal

 - support for reading default values and listing locks have been added
   to the dconf commandline tool

 - support for g_autoptr() has been added for DConfClient and
   DConfChangeset

 - the handling of reading of default values via GSettings has been made
   more efficient.  More major changes to the GSettings backend are
   expected in the near future.

Changes in dconf 0.24.0
========================

The version number was increased and a new entry was added to the NEWS.

Changes in dconf 0.23.2
========================

 - remove dconf-editor manpage (accidentally missed during the split)

 - fix whitespace issues in 'dconf --help'

Changes in dconf 0.23.1
========================

 - dconf-editor is now in a separate package

 - portability improvements


(prlw1)