checker: disallow struct int to ptr outside unsafe (#17923)

vlib/net/openssl/openssl_compiles_test.v

@@ -5,7 +5,7 @@ struct Abc {
 }
 
 fn test_printing_struct_with_reference_field_of_type_ssl_ctx() {
-	a := Abc{&C.SSL_CTX(123)}
+	a := unsafe { Abc{&C.SSL_CTX(123)} }
 	dump(a)
 	sa := a.str()
 	assert sa.contains('&C.SSL_CTX(0x7b)')

vlib/net/openssl/ssl_connection.v

@@ -436,7 +436,7 @@ fn @select(handle int, test Select, timeout time.Duration) !bool {
 	// infinite timeout is signaled by passing null as the timeout to
 	// select
 	if timeout == net.infinite_timeout {
-		timeval_timeout = &C.timeval(0)
+		timeval_timeout = &C.timeval(unsafe { nil })
 	}
 
 	match test {