When adding glue to the header, we add header to the wait-free stack to
be cleaned up later which sets wfc_node->next to non-NULL value. When
the actual cleaning happens we would only cleanup the .glue_list, but
since the database isn't locked for the time being, the headers could be
reused while cleaning the existing glue entries, which creates a data
race between database versions.
Revert the code back to use per-database-version hashtable where keys
are the node pointers. This allows each database version to have
independent glue cache table that doesn't affect nodes or headers that
could already "belong" to the future database version.
Add HTTPS, SVCB, SRV, PTR, NAPTR, DNSKEY and TXT records to the list of
the priority types that are put at the beginning of the slabheader list
for faster access and to avoid eviction when there are more types than
the max-types-per-name limit.
when the QPDB is implemented, we will need to have both qpdb_p.h and
rbtdb_p.h. in order to prevent name collisions or code duplication,
this commit adds a generic private header file, db_p.h, containing
structures and macros that will be used by both databases.
some functions and structs have been renamed to more specifically refer
to the RBT database, in order to avoid namespace collision with similar
things that will be needed by the QPDB later.
