g.parser: add missing header

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@71254 15284696-431f-4ddb-bdfa-cd5b030d7da7

general/g.parser/revoke.c

@@ -5,6 +5,7 @@
 
 #include "proto.h"
 
+#include <grass/spawn.h>
 #include <grass/glocale.h>
 
 int reinvoke_script(const struct context *ctx, const char *filename)