Cosmetic improvement: use BKI_DEFAULT and BKI_LOOKUP in pg_language.

The point of this is not really to remove redundancy in pg_language.dat;
with only three entries, it's hardly worth it.  Rather, it is to get
to a point where there are exactly zero hard-coded numeric pg_proc OID
references in the catalog .dat files.  The lanvalidator column was the
only remaining location of such references, and it seems like a good
thing for future-proofing reasons to make it not be a special case.

There are still a few places in the .dat files with numeric OID references
to other catalogs, but after review I don't see any that seem worth
changing at present.  In each case there are just too few entries to make
it worth the trouble to create lookup infrastructure.

This doesn't change the emitted postgres.bki file, so no catversion bump.

src/include/catalog/pg_language.dat

@@ -14,18 +14,12 @@
 
 { oid => '12', oid_symbol => 'INTERNALlanguageId',
   descr => 'built-in functions',
-  lanname => 'internal', lanowner => 'PGUID', lanispl => 'f',
-  lanpltrusted => 'f', lanplcallfoid => '0', laninline => '0',
-  lanvalidator => '2246', lanacl => '_null_' },
+  lanname => 'internal', lanvalidator => 'fmgr_internal_validator' },
 { oid => '13', oid_symbol => 'ClanguageId',
   descr => 'dynamically-loaded C functions',
-  lanname => 'c', lanowner => 'PGUID', lanispl => 'f', lanpltrusted => 'f',
-  lanplcallfoid => '0', laninline => '0', lanvalidator => '2247',
-  lanacl => '_null_' },
+  lanname => 'c', lanvalidator => 'fmgr_c_validator' },
 { oid => '14', oid_symbol => 'SQLlanguageId',
   descr => 'SQL-language functions',
-  lanname => 'sql', lanowner => 'PGUID', lanispl => 'f', lanpltrusted => 't',
-  lanplcallfoid => '0', laninline => '0', lanvalidator => '2248',
-  lanacl => '_null_' },
+  lanname => 'sql', lanpltrusted => 't', lanvalidator => 'fmgr_sql_validator' },
 
 ]

src/include/catalog/pg_language.h

@@ -28,16 +28,30 @@
  */
 CATALOG(pg_language,2612,LanguageRelationId)
 {
-	NameData	lanname;		/* Language name */
-	Oid			lanowner;		/* Language's owner */
-	bool		lanispl;		/* Is a procedural language */
-	bool		lanpltrusted;	/* PL is trusted */
-	Oid			lanplcallfoid;	/* Call handler for PL */
-	Oid			laninline;		/* Optional anonymous-block handler function */
-	Oid			lanvalidator;	/* Optional validation function */
+	/* Language name */
+	NameData	lanname;
+
+	/* Language's owner */
+	Oid			lanowner BKI_DEFAULT(PGUID);
+
+	/* Is a procedural language */
+	bool		lanispl BKI_DEFAULT(f);
+
+	/* PL is trusted */
+	bool		lanpltrusted BKI_DEFAULT(f);
+
+	/* Call handler, if it's a PL */
+	Oid			lanplcallfoid BKI_DEFAULT(0) BKI_LOOKUP(pg_proc);
+
+	/* Optional anonymous-block handler function */
+	Oid			laninline BKI_DEFAULT(0) BKI_LOOKUP(pg_proc);
+
+	/* Optional validation function */
+	Oid			lanvalidator BKI_DEFAULT(0) BKI_LOOKUP(pg_proc);
 
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
-	aclitem		lanacl[1];		/* Access privileges */
+	/* Access privileges */
+	aclitem		lanacl[1] BKI_DEFAULT(_null_);
 #endif
 } FormData_pg_language;