g10: Make the keyblock cache per-handle rather than global.
* g10/keydb.c (keyblock_cache): Don't declare this variable. Instead... (struct keyblock_cache): ... turn its type into this first class object... (struct keydb_handle): ... and instantiate it once per database handle. Update all users. (keydb_rebuild_caches): Don't invalidate the keyblock cache.
- Signed-off-by: Neal H. Walfield <neal@g10code.com>.