cmake HAVE_POOL_OF_THREADS examples

GreatSQL/GreatSQL sql/CMakeLists.txt :131

ADD_DEFINITIONS(-DMYSQL_SERVER -DHAVE_POOL_OF_THREADS)

percona/percona-server sql/CMakeLists.txt :115

ADD_DEFINITIONS(-DMYSQL_SERVER -DHAVE_POOL_OF_THREADS)

percona/percona-xtradb-cluster sql/CMakeLists.txt :115

ADD_DEFINITIONS(-DMYSQL_SERVER -DHAVE_POOL_OF_THREADS)