Modules compatibility: down flag promoted to a bitmask.

It is to be used as a bitmask with various bits set/reset when appropriate.
63b8b157b776 made a similar change to ngx_http_upstream_rr_peer_t.down and
ngx_stream_upstream_rr_peer_t.down.

src/http/ngx_http_upstream.h

diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index c552ac0..3e714e5 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -98,8 +98,8 @@
     ngx_uint_t                       max_fails;
     time_t                           fail_timeout;
     ngx_msec_t                       slow_start;
+    ngx_uint_t                       down;
 
-    unsigned                         down:1;
     unsigned                         backup:1;
 
     NGX_COMPAT_BEGIN(6)

src/stream/ngx_stream_upstream.h

diff --git a/src/stream/ngx_stream_upstream.h b/src/stream/ngx_stream_upstream.h
index 90076e0..73947f4 100644
--- a/src/stream/ngx_stream_upstream.h
+++ b/src/stream/ngx_stream_upstream.h
@@ -58,8 +58,8 @@
     ngx_uint_t                         max_fails;
     time_t                             fail_timeout;
     ngx_msec_t                         slow_start;
+    ngx_uint_t                         down;
 
-    unsigned                           down:1;
     unsigned                           backup:1;
 
     NGX_COMPAT_BEGIN(4)