Merge proxy_protocol setting of listen directives.

It's now enough to specify proxy_protocol option in one listen directive to
enable it in all servers listening on the same address/port.  Previously,
the setting from the first directive was always used.
diff --git a/src/http/ngx_http.c b/src/http/ngx_http.c
index 72981c1..924c4b5 100644
--- a/src/http/ngx_http.c
+++ b/src/http/ngx_http.c
@@ -1220,7 +1220,7 @@
 {
     u_char                *p;
     size_t                 len, off;
-    ngx_uint_t             i, default_server;
+    ngx_uint_t             i, default_server, proxy_protocol;
     struct sockaddr       *sa;
     ngx_http_conf_addr_t  *addr;
 #if (NGX_HAVE_UNIX_DOMAIN)
@@ -1281,6 +1281,8 @@
         /* preserve default_server bit during listen options overwriting */
         default_server = addr[i].opt.default_server;
 
+        proxy_protocol = lsopt->proxy_protocol || addr[i].opt.proxy_protocol;
+
 #if (NGX_HTTP_SSL)
         ssl = lsopt->ssl || addr[i].opt.ssl;
 #endif
@@ -1314,6 +1316,7 @@
         }
 
         addr[i].opt.default_server = default_server;
+        addr[i].opt.proxy_protocol = proxy_protocol;
 #if (NGX_HTTP_SSL)
         addr[i].opt.ssl = ssl;
 #endif