configure: add support for "--enable-poll"
configure: add support for "--enable-poll"

Conflicts:
	configure.ac

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