Handling of Content-Encoding set from perl.

This fixes double gzipping in case of gzip filter being enabled while perl
returns already gzipped response.

src/http/modules/perl/nginx.xs

diff --git a/src/http/modules/perl/nginx.xs b/src/http/modules/perl/nginx.xs
index c07118b..e3a9dd5 100644
--- a/src/http/modules/perl/nginx.xs
+++ b/src/http/modules/perl/nginx.xs
@@ -474,6 +474,13 @@
         r->headers_out.content_length = header;
     }
 
+    if (header->key.len == sizeof("Content-Encoding") - 1
+        && ngx_strncasecmp(header->key.data, "Content-Encoding",
+                           sizeof("Content-Encoding") - 1) == 0)
+    {
+        r->headers_out.content_encoding = header;
+    }
+
 
 void
 filename(r)