The change to reduce GConf trips by using
gconf_client_all_entries() broke the fallback to builtin values
because update_binding() was no longer called for bindings not
found in GConf. Fix this by keeping track of the bindings we
find from GConf in a hash table, then looping through and setting
all the bindings at the end.
This also improves efficiency by avoiding a linear scan for each
binding in GConf.
https://bugzilla.gnome.org/show_bug.cgi?id=609710