maint(gpg2john.c): add missing prototypes

The clang compiler was complaining with the error message: "Passing
arguments to a function without a prototype is deprecated in all
versions of C".

Signed-off-by: Claudio André <dev@claudioandre.slmail.me>

src/gpg2john.c

@@ -1208,7 +1208,7 @@ Private_Packet(int len)
  */
 
 
-typedef void (*funcptr)();
+typedef void (*funcptr)(int);
 
 private int get_new_len(int);
 private int is_partial(int);
@@ -1295,27 +1295,25 @@ TAG[] = {
 #define TAG_NUM (sizeof(TAG) * sizeof(string))
 
 private void
-(*tag_func[])() = {
-	Reserved,
-	Public_Key_Encrypted_Session_Key_Packet,
-	Signature_Packet,
-	Symmetric_Key_Encrypted_Session_Key_Packet,
-	One_Pass_Signature_Packet,
-	Secret_Key_Packet,
-	Public_Key_Packet,
-	Secret_Subkey_Packet,
-	Compressed_Data_Packet,
+(*tag_func[])(int, int, int, char *) = {
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
 	Symmetrically_Encrypted_Data_Packet,
-	Marker_Packet,
-	Literal_Data_Packet,
-	Trust_Packet,
-	User_ID_Packet,
-	Public_Subkey_Packet,
 	NULL,
 	NULL,
-	User_Attribute_Packet,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
 	Symmetrically_Encrypted_and_MDC_Packet,
-	Modification_Detection_Code_Packet,
 	NULL,
 	NULL,
 	NULL,
@@ -1357,10 +1355,11 @@ private void
 	NULL,
 	NULL,
 	NULL,
-	Private_Packet,
-	Private_Packet,
-	Private_Packet,
-	Private_Packet,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
+	NULL,
 };
 
 char *pkt_type(int tag) {