ap_should_client_block — ready to receive data from the client
int ap_should_client_block(request_rec *r)
Checks whether the client will send data and invites it to continue,
if necessary (by sending a 100
Continue response if the client is HTTP 1.1 or
higher). Returns 1 if the client should send data;
0 if not. ap_setup_client_block(
) should be called before this function, and this function
should be called before ap_ get_client_block().
This function should only be called once. It should also not be
called until we are ready to receive data from the client.