Add support for fetching some SAN types from X509 certificates

Note: valgrind complains about uninitialized data when UTF8Strings are passed to
ASN1_STRING_to_UTF8(), however the result is fine. Accessing the same data by
other means does not yield the error, I therefore suspect it a false positive.

src/X509Certificate.h

@@ -38,6 +38,7 @@
 - initWithStruct: (X509*)cert;
 - (OFDictionary*)issuer;
 - (OFDictionary*)subject;
+- (OFDictionary*)subjectAlternativeName;
 - (OFDictionary*)X509_dictionaryFromX509Name: (X509_NAME*)name;
 - (OFString*)X509_stringFromASN1Object: (ASN1_OBJECT*)obj;
 - (OFString*) X509_stringFromASN1String: (ASN1_STRING*)str;