MDEV-11707: Fix incorrect memset() for structures containing

dynamic class GenericPolicy<TTASEventMutex<GenericPolicy> >'; vtable

Instead using mem_heap_alloc and memset, use mem_heap_zalloc
directly.

storage/innobase/buf/buf0mtflu.cc

 /*****************************************************************************
 
 Copyright (C) 2013, 2014, Fusion-io. All Rights Reserved.
-Copyright (C) 2013, 2015, MariaDB Corporation. All Rights Reserved.
+Copyright (C) 2013, 2017, MariaDB Corporation. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -486,14 +486,13 @@ buf_mtflu_handler_init(
 	mtflush_heap2 = mem_heap_create(0);
 	ut_a(mtflush_heap2 != NULL);
 
-	mtflush_ctx = (thread_sync_t *)mem_heap_alloc(mtflush_heap,
+	mtflush_ctx = (thread_sync_t *)mem_heap_zalloc(mtflush_heap,
 				sizeof(thread_sync_t));
-	memset(mtflush_ctx, 0, sizeof(thread_sync_t));
+
 	ut_a(mtflush_ctx != NULL);
-	mtflush_ctx->thread_data = (thread_data_t*)mem_heap_alloc(
+	mtflush_ctx->thread_data = (thread_data_t*)mem_heap_zalloc(
 		mtflush_heap, sizeof(thread_data_t) * n_threads);
 	ut_a(mtflush_ctx->thread_data);
-	memset(mtflush_ctx->thread_data, 0, sizeof(thread_data_t) * n_threads);
 
 	mtflush_ctx->n_threads = n_threads;
 	mtflush_ctx->wq = ib_wqueue_create();

storage/xtradb/buf/buf0mtflu.cc

 /*****************************************************************************
 
 Copyright (C) 2013, 2014, Fusion-io. All Rights Reserved.
-Copyright (C) 2013, 2015, MariaDB Corporation. All Rights Reserved.
+Copyright (C) 2013, 2017, MariaDB Corporation. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -486,14 +486,13 @@ buf_mtflu_handler_init(
 	mtflush_heap2 = mem_heap_create(0);
 	ut_a(mtflush_heap2 != NULL);
 
-	mtflush_ctx = (thread_sync_t *)mem_heap_alloc(mtflush_heap,
+	mtflush_ctx = (thread_sync_t *)mem_heap_zalloc(mtflush_heap,
 				sizeof(thread_sync_t));
-	memset(mtflush_ctx, 0, sizeof(thread_sync_t));
+
 	ut_a(mtflush_ctx != NULL);
-	mtflush_ctx->thread_data = (thread_data_t*)mem_heap_alloc(
+	mtflush_ctx->thread_data = (thread_data_t*)mem_heap_zalloc(
 		mtflush_heap, sizeof(thread_data_t) * n_threads);
 	ut_a(mtflush_ctx->thread_data);
-	memset(mtflush_ctx->thread_data, 0, sizeof(thread_data_t) * n_threads);
 
 	mtflush_ctx->n_threads = n_threads;
 	mtflush_ctx->wq = ib_wqueue_create();