cmake HAVE_SENDTO examples

fluent/fluent-bit lib/c-ares-1.34.4/CMakeLists.txt :449 

CHECK_SYMBOL_EXISTS (sendto          "${CMAKE_EXTRA_INCLUDE_FILES}" HAVE_SENDTO)

ShadowsocksR-Live/shadowsocksr-native cmake/configure.cmake :137 

check_function_exists(sendto HAVE_SENDTO)