ITS#7598 Tweak MDB_<NEXT/PREV>_NODUP,fix mdb_stat.

MDB_NEXT_NODUP, MDB_PREV_NODUP: Allow for non-MDB_DUPSORT databases.
No mdb.c code changes needed.

mdb_stat.c: Use MDB_NEXT_NODUP, to avoid a crash with a DUPSORT mainDB.

libraries/liblmdb/lmdb.h

@@ -325,13 +325,11 @@ typedef enum MDB_cursor_op {
 								Only for #MDB_DUPSORT */
 	MDB_NEXT_MULTIPLE,		/**< Return all duplicate data items at the next
 								cursor position. Only for #MDB_DUPFIXED */
-	MDB_NEXT_NODUP,			/**< Position at first data item of next key.
-								Only for #MDB_DUPSORT */
+	MDB_NEXT_NODUP,			/**< Position at first data item of next key */
 	MDB_PREV,				/**< Position at previous data item */
 	MDB_PREV_DUP,			/**< Position at previous data item of current key.
 								Only for #MDB_DUPSORT */
-	MDB_PREV_NODUP,			/**< Position at last data item of previous key.
-								Only for #MDB_DUPSORT */
+	MDB_PREV_NODUP,			/**< Position at last data item of previous key */
 	MDB_SET,				/**< Position at specified key */
 	MDB_SET_KEY,			/**< Position at specified key, return key + data */
 	MDB_SET_RANGE			/**< Position at first key greater than or equal to specified key. */

libraries/liblmdb/mdb_stat.c

@@ -193,7 +193,7 @@ int main(int argc, char *argv[])
 			printf("mdb_cursor_open failed, error %d %s\n", rc, mdb_strerror(rc));
 			goto txn_abort;
 		}
-		while ((rc = mdb_cursor_get(cursor, &key, NULL, MDB_NEXT)) == 0) {
+		while ((rc = mdb_cursor_get(cursor, &key, NULL, MDB_NEXT_NODUP)) == 0) {
 			char *str = malloc(key.mv_size+1);
 			MDB_dbi db2;
 			memcpy(str, key.mv_data, key.mv_size);