crypto/rsa: support > 3 primes.

With full multi-prime support we can support version 1 PKCS#1 private
keys. This means exporting all the members of rsa.PrivateKey, thus
making the API a little messy. However there has already been another
request to export this so it seems to be something that's needed.

Over time, rsa.GenerateMultiPrimeKey will replace rsa.GenerateKey, but
I need to work on the prime balance first because we're no longer
generating primes which are a multiples of 8 bits.

Fixes #987.

R=rsc
CC=golang-dev
https://golang.org/cl/4378046

Author: agl

src/pkg/crypto/openpgp/packet/private_key.go

@@ -164,8 +164,10 @@ func (pk *PrivateKey) parseRSAPrivateKey(data []byte) (err os.Error) {
 	}
 
 	rsaPriv.D = new(big.Int).SetBytes(d)
-	rsaPriv.P = new(big.Int).SetBytes(p)
-	rsaPriv.Q = new(big.Int).SetBytes(q)
+	rsaPriv.Primes = make([]*big.Int, 2)
+	rsaPriv.Primes[0] = new(big.Int).SetBytes(p)
+	rsaPriv.Primes[1] = new(big.Int).SetBytes(q)
+	rsaPriv.Precompute()
 	pk.PrivateKey = rsaPriv
 	pk.Encrypted = false
 	pk.encryptedData = nil