Parser: parse into custom dive site table

To extend the undo system to dive sites, the importers and downloaders
must not parse directly into the global dive site table. Instead,
pass a dive_site_table argument to parse into.

For now, always pass the global dive_site_table so that this commit
should not cause any functional change.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/parse.h

@@ -60,6 +60,7 @@ struct parser_state {
 	struct units xml_parsing_units;
 	struct dive_table *target_table;	/* non-owning */
 	struct trip_table *trips;		/* non-owning */
+	struct dive_site_table *sites;		/* non-owning */
 
 	sqlite3 *sql_handle;			/* for SQL based parsers */
 	event_allocation_t event_allocation;