Magic blocks don't do us any good unless we use 'em ... so install one

in every shared library.

src/tutorial/complex.c

@@ -10,6 +10,8 @@
 #include "libpq/pqformat.h"		/* needed for send/recv functions */
 
 
+PG_MODULE_MAGIC;
+
 typedef struct Complex
 {
 	double		x;