cmake HAVE_SIGADDSET examples

arkdb/inception configure.cmake :470 

CHECK_FUNCTION_EXISTS (sigaddset HAVE_SIGADDSET)

alibaba/AliSQL configure.cmake :577 

CHECK_FUNCTION_EXISTS (sigaddset HAVE_SIGADDSET)

Tokutek/mysql-5.5 configure.cmake :410 

CHECK_FUNCTION_EXISTS (sigaddset HAVE_SIGADDSET)