Upstream: http_403 support in proxy_next_upstream (and friends).

The parameter is mostly identical to http_404, and is expected to
be used in similar situations.  The 403 code might be returned by
a backend instead of 404 on initial sync of new directories with rsync.

See here for feature request and additional details:
http://mailman.nginx.org/pipermail/nginx-ru/2013-April/050920.html
diff --git a/src/http/modules/ngx_http_fastcgi_module.c b/src/http/modules/ngx_http_fastcgi_module.c
index f386926..0b186d7 100644
--- a/src/http/modules/ngx_http_fastcgi_module.c
+++ b/src/http/modules/ngx_http_fastcgi_module.c
@@ -185,6 +185,7 @@
     { ngx_string("invalid_header"), NGX_HTTP_UPSTREAM_FT_INVALID_HEADER },
     { ngx_string("http_500"), NGX_HTTP_UPSTREAM_FT_HTTP_500 },
     { ngx_string("http_503"), NGX_HTTP_UPSTREAM_FT_HTTP_503 },
+    { ngx_string("http_403"), NGX_HTTP_UPSTREAM_FT_HTTP_403 },
     { ngx_string("http_404"), NGX_HTTP_UPSTREAM_FT_HTTP_404 },
     { ngx_string("updating"), NGX_HTTP_UPSTREAM_FT_UPDATING },
     { ngx_string("off"), NGX_HTTP_UPSTREAM_FT_OFF },
diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index d5cf07d..2cf0133 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -178,6 +178,7 @@
     { ngx_string("http_502"), NGX_HTTP_UPSTREAM_FT_HTTP_502 },
     { ngx_string("http_503"), NGX_HTTP_UPSTREAM_FT_HTTP_503 },
     { ngx_string("http_504"), NGX_HTTP_UPSTREAM_FT_HTTP_504 },
+    { ngx_string("http_403"), NGX_HTTP_UPSTREAM_FT_HTTP_403 },
     { ngx_string("http_404"), NGX_HTTP_UPSTREAM_FT_HTTP_404 },
     { ngx_string("updating"), NGX_HTTP_UPSTREAM_FT_UPDATING },
     { ngx_string("off"), NGX_HTTP_UPSTREAM_FT_OFF },
diff --git a/src/http/modules/ngx_http_scgi_module.c b/src/http/modules/ngx_http_scgi_module.c
index 49cc96d..e8f822c 100644
--- a/src/http/modules/ngx_http_scgi_module.c
+++ b/src/http/modules/ngx_http_scgi_module.c
@@ -65,6 +65,7 @@
     { ngx_string("invalid_header"), NGX_HTTP_UPSTREAM_FT_INVALID_HEADER },
     { ngx_string("http_500"), NGX_HTTP_UPSTREAM_FT_HTTP_500 },
     { ngx_string("http_503"), NGX_HTTP_UPSTREAM_FT_HTTP_503 },
+    { ngx_string("http_403"), NGX_HTTP_UPSTREAM_FT_HTTP_403 },
     { ngx_string("http_404"), NGX_HTTP_UPSTREAM_FT_HTTP_404 },
     { ngx_string("updating"), NGX_HTTP_UPSTREAM_FT_UPDATING },
     { ngx_string("off"), NGX_HTTP_UPSTREAM_FT_OFF },
diff --git a/src/http/modules/ngx_http_uwsgi_module.c b/src/http/modules/ngx_http_uwsgi_module.c
index 623ee49..b8bee86 100644
--- a/src/http/modules/ngx_http_uwsgi_module.c
+++ b/src/http/modules/ngx_http_uwsgi_module.c
@@ -78,6 +78,7 @@
     { ngx_string("invalid_header"), NGX_HTTP_UPSTREAM_FT_INVALID_HEADER },
     { ngx_string("http_500"), NGX_HTTP_UPSTREAM_FT_HTTP_500 },
     { ngx_string("http_503"), NGX_HTTP_UPSTREAM_FT_HTTP_503 },
+    { ngx_string("http_403"), NGX_HTTP_UPSTREAM_FT_HTTP_403 },
     { ngx_string("http_404"), NGX_HTTP_UPSTREAM_FT_HTTP_404 },
     { ngx_string("updating"), NGX_HTTP_UPSTREAM_FT_UPDATING },
     { ngx_string("off"), NGX_HTTP_UPSTREAM_FT_OFF },
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 85fc849..16e6602 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -369,6 +369,7 @@
     { 502, NGX_HTTP_UPSTREAM_FT_HTTP_502 },
     { 503, NGX_HTTP_UPSTREAM_FT_HTTP_503 },
     { 504, NGX_HTTP_UPSTREAM_FT_HTTP_504 },
+    { 403, NGX_HTTP_UPSTREAM_FT_HTTP_403 },
     { 404, NGX_HTTP_UPSTREAM_FT_HTTP_404 },
     { 0, 0 }
 };
@@ -3156,8 +3157,11 @@
 
     if (u->peer.sockaddr) {
 
-        if (ft_type == NGX_HTTP_UPSTREAM_FT_HTTP_404) {
+        if (ft_type == NGX_HTTP_UPSTREAM_FT_HTTP_403
+            || ft_type == NGX_HTTP_UPSTREAM_FT_HTTP_404)
+        {
             state = NGX_PEER_NEXT;
+
         } else {
             state = NGX_PEER_FAILED;
         }
@@ -3189,6 +3193,10 @@
             status = NGX_HTTP_INTERNAL_SERVER_ERROR;
             break;
 
+        case NGX_HTTP_UPSTREAM_FT_HTTP_403:
+            status = NGX_HTTP_FORBIDDEN;
+            break;
+
         case NGX_HTTP_UPSTREAM_FT_HTTP_404:
             status = NGX_HTTP_NOT_FOUND;
             break;
diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index 29ebf9b..fd4e36b 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -24,10 +24,11 @@
 #define NGX_HTTP_UPSTREAM_FT_HTTP_502        0x00000020
 #define NGX_HTTP_UPSTREAM_FT_HTTP_503        0x00000040
 #define NGX_HTTP_UPSTREAM_FT_HTTP_504        0x00000080
-#define NGX_HTTP_UPSTREAM_FT_HTTP_404        0x00000100
-#define NGX_HTTP_UPSTREAM_FT_UPDATING        0x00000200
-#define NGX_HTTP_UPSTREAM_FT_BUSY_LOCK       0x00000400
-#define NGX_HTTP_UPSTREAM_FT_MAX_WAITING     0x00000800
+#define NGX_HTTP_UPSTREAM_FT_HTTP_403        0x00000100
+#define NGX_HTTP_UPSTREAM_FT_HTTP_404        0x00000200
+#define NGX_HTTP_UPSTREAM_FT_UPDATING        0x00000400
+#define NGX_HTTP_UPSTREAM_FT_BUSY_LOCK       0x00000800
+#define NGX_HTTP_UPSTREAM_FT_MAX_WAITING     0x00001000
 #define NGX_HTTP_UPSTREAM_FT_NOLIVE          0x40000000
 #define NGX_HTTP_UPSTREAM_FT_OFF             0x80000000
 
@@ -35,6 +36,7 @@
                                              |NGX_HTTP_UPSTREAM_FT_HTTP_502  \
                                              |NGX_HTTP_UPSTREAM_FT_HTTP_503  \
                                              |NGX_HTTP_UPSTREAM_FT_HTTP_504  \
+                                             |NGX_HTTP_UPSTREAM_FT_HTTP_403  \
                                              |NGX_HTTP_UPSTREAM_FT_HTTP_404)
 
 #define NGX_HTTP_UPSTREAM_INVALID_HEADER     40