Use the "extern" keyword in function declarations

Author: johto

pgspeck.h

@@ -3,9 +3,9 @@
 
 #include "postgres.h"
 
-uint32 speck_encrypt32(const uint32 xy, const int64 K);
-uint32 speck_decrypt32(const uint32 xy, const int64 K);
-int64 speck_encrypt48(const int64 xy, const int64 *K);
-int64 speck_decrypt48(const int64 xy, const int64 *K);
+extern uint32 speck_encrypt32(const uint32 xy, const int64 K);
+extern uint32 speck_decrypt32(const uint32 xy, const int64 K);
+extern int64 speck_encrypt48(const int64 xy, const int64 *K);
+extern int64 speck_decrypt48(const int64 xy, const int64 *K);
 
 #endif