Add header with extern function prototypes

src/spicelib/devices/cpl/cplhash.h

@@ -0,0 +1,12 @@
+/**********
+Copyright 2021 The ngspice team  All rights
+reserved.
+Author: 2021 Holger Vogt
+3-clause BSD license
+**********/
+
+/* cplhash.c */
+extern void mem_init(void);
+extern void mem_delete(void);
+extern int memsaved(void *ptr);
+extern void memdeleted(const void *ptr);

src/spicelib/devices/cpl/cplsetup.c

@@ -13,6 +13,7 @@ Modified: 2004 Paolo Nenzi - (ng)spice integration
 #include "ngspice/suffix.h"
 
 #include "ngspice/multi_line.h"
+#include "cplhash.h"