Improved handling of blackboxes

[wzab]

Current implementation incorrectly handles the situation when the same blackbox is instantiated a few times with different addrbits. In fact the first instance defines the addrbits for the generated C header and probably for other files.
The better solution could be requiring a single declaration of the blackbox with addrbits (and optionally also the path to the XML address map?) and then using so defined blackbox:

<blackbox name="BB1" addrbits=12 xmlpath="../BB1.xml" />
<block name="AnyBlock">
     ...
     <subblock name="BB1_Instance1" type="BB1" />
     <subblock name=Instance_2" type="BB2" />
     ...
</block>