Bump PG_CONTROL_VERSION for previous 9.4 changes.

This should have been done in 6bc8ef0b
and/or 50e54709, but better late than
never.  If we don't change this then we risk 9.3 pg_controldata or
pg_resetxlog being inappropriately used against a 9.4 pg_control file,
or vice versa.

src/include/catalog/pg_control.h

@@ -21,7 +21,7 @@
 
 
 /* Version identifier for this pg_control format */
-#define PG_CONTROL_VERSION	937
+#define PG_CONTROL_VERSION	941
 
 /*
  * Body of CheckPoint XLOG records.  This is declared here because we keep