cmake HAVE_SIGHOLD examples

arkdb/inception configure.cmake :472 

CHECK_FUNCTION_EXISTS (sighold HAVE_SIGHOLD)

alibaba/AliSQL configure.cmake :579 

CHECK_FUNCTION_EXISTS (sighold HAVE_SIGHOLD)

Tokutek/mysql-5.5 configure.cmake :412 

CHECK_FUNCTION_EXISTS (sighold HAVE_SIGHOLD)