Support a dynamic module with nginx

feature: this module can now be built as a "dynamic module"  via the --add-dynamic-module=PATH option of ./configure.

Author: khavishbhundoo

config

@@ -2,5 +2,14 @@ USE_MD5=YES
 USE_SHA1=YES
 USE_OPENSSL=YES
 ngx_addon_name=ngx_http_upload_module
-HTTP_MODULES="$HTTP_MODULES ngx_http_upload_module"
-NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ngx_addon_dir/ngx_http_upload_module.c"
+
+if test -n "$ngx_module_link"; then
+    ngx_module_type=HTTP
+    ngx_module_name=$ngx_addon_name
+    ngx_module_srcs="$ngx_addon_dir/ngx_http_upload_module.c"
+
+    . auto/module
+else
+    HTTP_MODULES="$HTTP_MODULES ngx_http_upload_module"
+    NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ngx_addon_dir/ngx_http_upload_module.c"
+fi