package/libmicrohttpd: mark as broken on Nios II, infamous _gp issue

Fixes
http://autobuild.buildroot.net/results/76f/76f838b2b33311897f3c2ce82a65f3b73af2c046/



Propagate reverse dependency to janus-gateway. I did not propagate the
reverse dependency to kodi, ola and systemd because they are not
available for nios.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>