WL#7315 Optimizer cost model: main memory management of cost constants

Follow-up change:

WL#7315 moved the opt_costmodel unit test from being linked into the
unit tests linked without server to the unit tests that are linked
with server libraries. Due to this change, the sql/opt_costmodel.cc
file is no longer needed in the sqlgunitlib library.

Author: Olav Sandstaa

sql/CMakeLists.txt

@@ -347,7 +347,6 @@ ADD_DEPENDENCIES(slave GenError)
 SET(SQL_GUNIT_LIB_SOURCE 
   filesort_utils.cc 
   mdl.cc 
-  opt_costmodel.cc
   sql_list.cc 
   ../sql-common/sql_string.cc
   thr_malloc.cc

unittest/gunit/fake_costmodel.cc

@@ -19,6 +19,10 @@
 
 #include "fake_costmodel.h"
 
+Cost_model_server::~Cost_model_server()
+{
+}
+
 const double Server_cost_constants::KEY_COMPARE_COST= 0.1;
 const double Server_cost_constants::MEMORY_TEMPTABLE_CREATE_COST= 2.0;
 const double Server_cost_constants::MEMORY_TEMPTABLE_ROW_COST= 0.2;