Move the InnoDB Plugin tests from storage/innodb_plugin/mysql-test/ where

they are ignored to a new test suite "innodb_plugin".

Remove a hack in mtr that was deployed to run the builtin InnoDB tests against
the InnoDB Plugin. Also detect if a test is an 'innodb plugin test' and if so
then transparently replace the builtin InnoDB with the InnoDB Plugin.

mysql-test/suite/innodb_plugin/t/innodb_bug35220.test

@@ -0,0 +1,16 @@
+#
+# Bug#35220 ALTER TABLE too picky on reserved word "foreign"
+# http://bugs.mysql.com/35220
+#
+
+-- source include/have_innodb_plugin.inc
+
+SET storage_engine=InnoDB;
+
+# we care only that the following SQL commands do not produce errors
+-- disable_query_log
+-- disable_result_log
+
+CREATE TABLE bug35220 (foreign_col INT, dummy_cant_delete_all_columns INT);
+ALTER TABLE bug35220 DROP foreign_col;
+DROP TABLE bug35220;