Fix for "return 202" not discarding body.

Big POST (not fully preread) to a

    location / {
        return 202;
    }

resulted in incorrect behaviour due to "return" code path not calling
ngx_http_discard_request_body().  The same applies to all "return" used
with 2xx/3xx codes except 201 and 204, and to all "return ... text" uses.

Fix is to add ngx_http_discard_request_body() call to ngx_http_send_response()
function where it looks appropriate.  Discard body call from emtpy gif module
removed as it's now redundant.

Reported by Pyry Hakulinen, see
http://mailman.nginx.org/pipermail/nginx/2011-August/028503.html

src/http/modules/ngx_http_empty_gif_module.c

@@ -111,19 +111,12 @@ static ngx_str_t  ngx_http_gif_type = ngx_string("image/gif");
 static ngx_int_t
 ngx_http_empty_gif_handler(ngx_http_request_t *r)
 {
-    ngx_int_t                 rc;
     ngx_http_complex_value_t  cv;
 
     if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD))) {
         return NGX_HTTP_NOT_ALLOWED;
     }
 
-    rc = ngx_http_discard_request_body(r);
-
-    if (rc != NGX_OK) {
-        return rc;
-    }
-
     ngx_memzero(&cv, sizeof(ngx_http_complex_value_t));
 
     cv.value.len = sizeof(ngx_empty_gif);

src/http/ngx_http_core_module.c

@@ -1784,6 +1784,10 @@ ngx_http_send_response(ngx_http_request_t *r, ngx_uint_t status,
     ngx_buf_t    *b;
     ngx_chain_t   out;
 
+    if (ngx_http_discard_request_body(r) != NGX_OK) {
+        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    }
+
     r->headers_out.status = status;
 
     if (status == NGX_HTTP_NO_CONTENT) {