Fixed URI normalization with merge_slashes switched off.

Previously, "/foo///../bar" was normalized into "/foo/bar"
instead of "/foo//bar".
diff --git a/src/http/ngx_http_parse.c b/src/http/ngx_http_parse.c
index ed5cf75..aa56b97 100644
--- a/src/http/ngx_http_parse.c
+++ b/src/http/ngx_http_parse.c
@@ -1471,7 +1471,7 @@
             case '/':
             case '?':
             case '#':
-                u -= 5;
+                u -= 4;
                 for ( ;; ) {
                     if (u < r->uri.data) {
                         return NGX_HTTP_PARSE_INVALID_REQUEST;
@@ -1575,7 +1575,7 @@
         u--;
 
     } else if (state == sw_dot_dot) {
-        u -= 5;
+        u -= 4;
 
         for ( ;; ) {
             if (u < r->uri.data) {