HPACK patch broken for Nginx 1.13.6

Seems Nginx 1.13.6 update broken HPACK patch https://community.centminmod.com/threads/nginx-announce-nginx-1-13-6.13079/#post-55493

```
-o objs/src/http/ngx_http_postpone_filter_module.o \
src/http/ngx_http_postpone_filter_module.c
src/http/v2/ngx_http_v2_filter_module.c: In function ‘ngx_http_v2_header_filter’:
src/http/v2/ngx_http_v2_filter_module.c:137:32: error: redeclaration of ‘h2c’ with no linkage
ngx_http_v2_connection_t *h2c;
^~~
src/http/v2/ngx_http_v2_filter_module.c:133:32: note: previous declaration of ‘h2c’ was here
ngx_http_v2_connection_t *h2c;
^~~
make[1]: *** [objs/src/http/v2/ngx_http_v2_filter_module.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make[1]: Leaving directory `/svr-setup/nginx-1.13.6'
make: *** [build] Error 2
```
after disabling HPACK patch, Nginx 1.13.6 compiled fine on CentOS 6.9 64bit

```
nginx -V
nginx version: nginx/1.13.6
built by gcc 6.3.1 20170216 (Red Hat 6.3.1-3) (GCC)
built with OpenSSL 1.1.0f 25 May 2017
TLS SNI support enabled
```
> configure arguments: --with-ld-opt='-ljemalloc -Wl,-z,relro -Wl,-rpath,/usr/local/lib' --with-cc-opt='-m64 -march=native -DTCP_FASTOPEN=23 -g -O3 -fstack-protector-strong -flto -fuse-ld=gold --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -gsplit-dwarf' --sbin-path=/usr/local/sbin/nginx --conf-path=/usr/local/nginx/conf/nginx.conf --with-compat --with-http_stub_status_module --with-http_secure_link_module --with-libatomic --with-http_gzip_static_module --add-dynamic-module=../ngx_pagespeed-1.12.34.3-stable --with-http_sub_module --with-http_addition_module --with-http_image_filter_module=dynamic --with-http_geoip_module=dynamic --with-stream_geoip_module=dynamic --with-stream_realip_module --with-stream_ssl_preread_module --with-threads --with-stream=dynamic --with-stream_ssl_module --with-http_realip_module --add-dynamic-module=../ngx-fancyindex-0.4.2 --add-module=../ngx_cache_purge-2.4.2 --add-module=../ngx_devel_kit-0.3.0 --add-dynamic-module=../set-misc-nginx-module-0.31 --add-dynamic-module=../echo-nginx-module-0.61 --add-module=../redis2-nginx-module-0.14 --add-module=../ngx_http_redis-0.3.7 --add-module=../memc-nginx-module-0.18 --add-module=../srcache-nginx-module-0.31 --add-dynamic-module=../headers-more-nginx-module-0.32 --with-pcre=../pcre-8.41 --with-pcre-jit --with-zlib=../zlib-1.2.11 --with-http_ssl_module --with-http_v2_module --with-openssl=../openssl-1.1.0f --with-openssl-opt='enable-ec_nistp_64_gcc_128'