Put server Unix sockets into /var/run/postgresql/ by default

Forwarded: No, Debian specific configuration with postgresql-common
Using /tmp for sockets allows everyone to spoof a PostgreSQL server. Thus use
/var/run/postgresql/ for "system" clusters which run as 'postgres' (user
clusters will still use /tmp). Since system cluster are by far the common case,
set it as default.


Gbp-Pq: Name 51-default-sockets-in-var.patch

src/include/pg_config_manual.h

@@ -179,7 +179,7 @@
  * here's where to twiddle it.  You can also override this at runtime
  * with the postmaster's -k switch.
  */
-#define DEFAULT_PGSOCKET_DIR  "/tmp"
+#define DEFAULT_PGSOCKET_DIR  "/var/run/postgresql"
 
 /*
  * This is the default event source for Windows event log.