Add more features in BCertificate class

* Make it possible to extract more useful data from the certificate
* Also get the OpenSSL error message when a certificate can't be
validated. Send it to the verification failure callback so it can be
shown to the user.

headers/os/net/Certificate.h

@@ -14,12 +14,19 @@ class BCertificate {
 public:
 				~BCertificate();
 
-	BString		String();
+	int			Version();
 
 	time_t		StartDate();
 	time_t		ExpirationDate();
+
+	bool		IsValidAuthority();
+	bool		IsSelfSigned();
+
 	BString		Issuer();
 	BString		Subject();
+	BString		SignatureAlgorithm();
+
+	BString		String();
 
 private:
 	friend class BSecureSocket::Private;

headers/os/net/SecureSocket.h

@@ -21,7 +21,7 @@ public:
 	virtual						~BSecureSocket();
 
 	virtual bool				CertificateVerificationFailed(BCertificate&
-									certificate);
+									certificate, const char* message);
 
 	// BSocket implementation