cmake HAVE_SIGTHREADMASK examples

arkdb/inception configure.cmake :468 

CHECK_FUNCTION_EXISTS (sigthreadmask HAVE_SIGTHREADMASK)

alibaba/AliSQL configure.cmake :575 

CHECK_FUNCTION_EXISTS (sigthreadmask HAVE_SIGTHREADMASK)

Tokutek/mysql-5.5 configure.cmake :408 

CHECK_FUNCTION_EXISTS (sigthreadmask HAVE_SIGTHREADMASK)