MDEV-34392 Inplace algorithm violates the foreign key constraint

- Fix the compilation error in gcc-5

sql/table.h

@@ -1927,7 +1927,14 @@ public:
     DBUG_ASSERT(fields_nullable);
     DBUG_ASSERT(field < n_fields);
     size_t bit= size_t{field} + referenced * n_fields;
-    fields_nullable[bit / 8]|= (unsigned char)(1 << (bit % 8));
+#if defined __GNUC__ && __GNUC__ == 5
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wconversion"
+#endif
+    fields_nullable[bit / 8]|= static_cast<unsigned char>(1 << (bit % 8));
+#if defined __GNUC__ && __GNUC__ == 5
+# pragma GCC diagnostic pop
+#endif
   }
 
   /**
@@ -1944,7 +1951,7 @@ public:
     unsigned n_field= get_n_fields();
     DBUG_ASSERT(field < n_field);
     size_t bit= size_t{field} + referenced * n_field;
-    return fields_nullable[bit / 8] & (1 << (bit % 8));
+    return fields_nullable[bit / 8] & (1U << (bit % 8));
   }
 
 } FOREIGN_KEY_INFO;

storage/innobase/handler/ha_innodb.cc

@@ -12518,7 +12518,10 @@ create_table_info_t::create_foreign_keys()
 				}
 			}
 		}
-
+#if defined __GNUC__ && __GNUC__ == 5
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wconversion"
+#endif
 		switch (fk->delete_opt) {
 		case FK_OPTION_UNDEF:
 		case FK_OPTION_RESTRICT:
@@ -12560,6 +12563,9 @@ create_table_info_t::create_foreign_keys()
 			ut_ad(0);
 			break;
 		}
+#if defined __GNUC__ && __GNUC__ == 5
+# pragma GCC diagnostic pop
+#endif
 	}
 
 	if (dict_foreigns_has_s_base_col(local_fk_set, table)) {

storage/innobase/handler/handler0alter.cc

@@ -2807,6 +2807,10 @@ innobase_set_foreign_key_option(
 		break;
 	}
 
+#if defined __GNUC__ && __GNUC__ == 5
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wconversion"
+#endif
 	switch (fk_key->update_opt) {
 	case FK_OPTION_NO_ACTION:
 	case FK_OPTION_RESTRICT:
@@ -2823,6 +2827,9 @@ innobase_set_foreign_key_option(
 		break;
 	}
 
+#if defined __GNUC__ && __GNUC__ == 5
+# pragma GCC diagnostic pop
+#endif
 	return(innobase_check_fk_option(foreign));
 }