Fixed bug in multi-table-delete code

client/mysqltest.c:
  Added --big-test argument
libmysqld/lib_sql.cc:
  Reset error messages before new query.
libmysqld/lib_vio.c:
  Fixed reading of results.
mysql-test/mysql-test-run.sh:
  Added option --big
mysql-test/r/multi_update.result:
  More multi-delete tests
mysql-test/t/bdb-crash.test:
  Added missing test if BDB is supported
mysql-test/t/multi_update.test:
  More multi-delete tests

mysql-test/mysql-test-run.sh

@@ -151,6 +151,8 @@ while test $# -gt 0; do
       DO_BENCH=1
       NO_SLAVE=1
       ;;  
+    --big*)			# Actually --big-test
+      EXTRA_MYSQL_TEST_OPT="$EXTRA_MYSQL_TEST_OPT $1" ;;
     --sleep=*)
       EXTRA_MYSQL_TEST_OPT="$EXTRA_MYSQL_TEST_OPT $1"
       SLEEP_TIME=`$ECHO "$1" | $SED -e "s;--sleep=;;"`