Proxy: fixed upstream search by proxy_pass with variables.

If "proxy_pass" is specified with variables, the resulting
hostname is looked up in the list of upstreams defined in
configuration.  The search was case-sensitive, as opposed
to the case of "proxy_pass" specified without variables.

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 0524144..26b5764 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -612,7 +612,7 @@
             if (uscf->host.len == host->len
                 && ((uscf->port == 0 && u->resolved->no_port)
                      || uscf->port == u->resolved->port)
-                && ngx_memcmp(uscf->host.data, host->data, host->len) == 0)
+                && ngx_strncasecmp(uscf->host.data, host->data, host->len) == 0)
             {
                 goto found;
             }