allow to append charset to the "Content-Type" header

src/http/modules/perl/nginx.xs

diff --git a/src/http/modules/perl/nginx.xs b/src/http/modules/perl/nginx.xs
index 7423daa..fdaedd7 100644
--- a/src/http/modules/perl/nginx.xs
+++ b/src/http/modules/perl/nginx.xs
@@ -131,6 +131,8 @@
             XSRETURN_EMPTY;
         }
 
+        r->headers_out.content_type_len = r->headers_out.content_type.len;
+
     } else {
         if (ngx_http_set_content_type(r) != NGX_OK) {
             XSRETURN_EMPTY;