Fixed false compiler warning.

Newer gcc versions (4.7+) report possible use of uninitialized variable if
nginx is being compiled with -O3.

src/http/ngx_http_request.c

diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index a0e6fad..0bb1b8c 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -1944,6 +1944,10 @@
     ngx_http_core_loc_conf_t  *clcf;
     ngx_http_core_srv_conf_t  *cscf;
 
+#if (NGX_SUPPRESS_WARN)
+    cscf = NULL;
+#endif
+
     hc = r->http_connection;
 
 #if (NGX_HTTP_SSL && defined SSL_CTRL_SET_TLSEXT_HOSTNAME)