libnm: include "glib.h" in "nm-version.h"

This is a forward port of commit 6f616d4c4b
which added this patch on nm-1-0 branch.

However, the reason stated there is wrong because we don't need this
to fix Qt examples. Building Qt examples was fixed in that "nm-dbus-interface.h"
no longer drags in "nm-version.h".

On the other hand, we still want "nm-version.h" to be self-contained,
and include "glib.h" as it needs it.

libnm-core/nm-version.h.in

@@ -21,6 +21,8 @@
 #ifndef NM_VERSION_H
 #define NM_VERSION_H
 
+#include <glib.h>
+
 /**
  * NM_MAJOR_VERSION:
  *

libnm-util/nm-version.h.in

@@ -21,6 +21,8 @@
 #ifndef NM_VERSION_H
 #define NM_VERSION_H
 
+#include <glib.h>
+
 /**
  * NM_MAJOR_VERSION:
  *