Updated NGINX 1.9.15 SPDY Patch

This updates the 1.9.7 patch to work with NGINX 1.9.15 and also fixes
two problem with the previous patch, that did not re-enable spdy directives
that were marked as deprecated by the http2 module and failed to compile
when the http2 module was enabled and spdy was disabled.

Author: felixbuenemann