Remove dead stuff from pgcrypto.

pgp-pubkey-DISABLED test has been unused since 2006, when support for
built-in bignum math was added (commit 1abf76e8). pgp-encrypt-DISABLED has
been unused forever, AFAICS.

Also remove a couple of unused error codes.

contrib/pgcrypto/expected/pgp-encrypt-DISABLED.out

--- no random source

contrib/pgcrypto/expected/pgp-pubkey-DISABLED.out

--- no bignum support

contrib/pgcrypto/px.c

@@ -67,12 +67,8 @@ static const struct error_desc px_err_list[] = {
 	{PXE_PGP_COMPRESSION_ERROR, "Compression error"},
 	{PXE_PGP_NOT_TEXT, "Not text data"},
 	{PXE_PGP_UNEXPECTED_PKT, "Unexpected packet in key data"},
-	{PXE_PGP_NO_BIGNUM,
-		"public-key functions disabled - "
-	"pgcrypto needs OpenSSL for bignums"},
 	{PXE_PGP_MATH_FAILED, "Math operation failed"},
 	{PXE_PGP_SHORT_ELGAMAL_KEY, "Elgamal keys must be at least 1024 bits long"},
-	{PXE_PGP_RSA_UNSUPPORTED, "pgcrypto does not support RSA keys"},
 	{PXE_PGP_UNKNOWN_PUBALGO, "Unknown public-key encryption algorithm"},
 	{PXE_PGP_WRONG_KEY, "Wrong key"},
 	{PXE_PGP_MULTIPLE_KEYS,

contrib/pgcrypto/px.h

@@ -88,10 +88,10 @@ void		px_free(void *p);
 #define PXE_PGP_COMPRESSION_ERROR	-105
 #define PXE_PGP_NOT_TEXT			-106
 #define PXE_PGP_UNEXPECTED_PKT		-107
-#define PXE_PGP_NO_BIGNUM			-108
+/* -108 is unused */
 #define PXE_PGP_MATH_FAILED			-109
 #define PXE_PGP_SHORT_ELGAMAL_KEY	-110
-#define PXE_PGP_RSA_UNSUPPORTED		-111
+/* -111 is unused */
 #define PXE_PGP_UNKNOWN_PUBALGO		-112
 #define PXE_PGP_WRONG_KEY			-113
 #define PXE_PGP_MULTIPLE_KEYS		-114

contrib/pgcrypto/sql/pgp-encrypt-DISABLED.sql

--- no random source

contrib/pgcrypto/sql/pgp-pubkey-DISABLED.sql

--- no bignum support