Fix Base 64 signature size calculation. If the signature byte size is not equally dividable by three the base 64 encoding needs three additional bytes. The value is now fixed to avoid such errors in the future.

<!DOCTYPE RCC><RCC version="1.0">
<qresource prefix="/certs">
    <file alias="ssl-certificate">certificates/ssl-test.der</file>
</qresource>
</RCC>