[gnome-multi-writer] trivial: Fix -Wimplicit-function-declaration warning

[Richard Hughes <rhughes src gnome org>]

commit b695de9f8b0219da0e740f46e024350c41bc99c8
Author: Richard Hughes <richard hughsie com>
Date:   Mon Aug 29 11:52:11 2016 +0100

    trivial: Fix -Wimplicit-function-declaration warning

 src/gmw-main.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/gmw-main.c b/src/gmw-main.c
index f50d6cf..c824724 100644
--- a/src/gmw-main.c
+++ b/src/gmw-main.c
@@ -32,6 +32,7 @@
 #include <locale.h>
 #include <stdlib.h>
 #include <udisks/udisks.h>
+#include <polkit/polkit.h>
 
 #include "gmw-cleanup.h"
 #include "gmw-device.h"