Fix compilation with ICC: missing "public" keyword in declaration

This change is correct. GCC wrongly accepted S60CertificateExtension
as covariant with Botan::Certificate_Extension even though the base
was inaccessible.

Reviewed-By: dt

src/plugins/qt4projectmanager/qt-s60/s60symbiancertificate.cpp

@@ -67,7 +67,7 @@ namespace {
 /*
 * X.509 S60 Certificate Extension
 */
-class S60CertificateExtension : Certificate_Extension
+class S60CertificateExtension : public Certificate_Extension
 {
 public:
     OID oid_of() const;