Upgrade: use socketpair only in non-blocking mode
Upgrade: use socketpair only in non-blocking mode

maru/libmicrohttpd-http2,maru/libmicrohttpd-http2,ghaderer/libmicrohttpd,maru/libmicrohttpd-http2,ghaderer/libmicrohttpd,ghaderer/libmicrohttpd