message: Add missing prediacte on Windows
diff: @@ -61,6 +61,11 @@ bool cc_not_minus1(int value) {
  fun_name, last_socket_error_as_string())
  #ifdef CAF_WINDOWS
  +// predicate for `ccall` meaning "expected result of f is a valid socket"
  +bool cc_valid_socket(caf::io::network::native_socket fd) {
  + return fd != caf::io::network::invalid_native_socket;
  +}
  +
  // calls a C functions and calls exit() if `predicate(var)` returns false
  #define CALL_CRITICAL_CFUN(var, predicate, funname, expr) \
  auto var = expr; \
  