dbmi: add missing header (https://trac.osgeo.org/grass/changeset/47937)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@47946 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/db/dbmi_client/shutdown.c

@@ -20,6 +20,7 @@
 #include <sys/wait.h>
 #endif
 #include <grass/dbmi.h>
+#include <grass/spawn.h>
 #include "macros.h"
 
 /*!
@@ -38,9 +39,6 @@
 */
 int db_shutdown_driver(dbDriver * driver)
 {
-#ifndef __MINGW32__
-    int pid;
-#endif
     int status;
 
 #ifdef __MINGW32__