package/libmicrohttpd: bump to version 0.9.66

See https://lists.gnu.org/archive/html/libmicrohttpd/2019-08/msg00000.html



Signed-off-by: Pierre-Jean Texier <pjtexier@koncepto.io>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>