Fix incorrect usmAESPrivProtocol import in nut-scanner

[Bi11]

In libnetsnmp, usmAES128PrivProtocol is a pointer, while usmAESPrivProtocol is an array.
This change is the same as in c7cf507.

[Bi11]

usmAES128PrivProtocol and usmAESPrivProtocol are NOT exchangeable in binary level.

Symbol table '.dynsym' contains 1302 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
   ...
   833: 00000000000b81e0     8 OBJECT  GLOBAL DEFAULT   24 usmAES128PrivProtocol
   ...
   178: 00000000000b7ce0    80 OBJECT  GLOBAL DEFAULT   24 usmAESPrivProtocol

[jimklimov]

I'm not at code at the moment; should other changes from that commit (lengths etc) apply here?

[Bi11]

The length is correct ( it was fixed in 54a6165 ).
But current code won't compile with old version of libnetsnmp which hasusmAES128PrivProtocol defined but no usmAESPrivProtocol.
But it is another task to fix compile issue with old version of libnetsnmp.

[jimklimov]

Thanks for the research and the fix.

If the older dependencies are relevant in practice, a (configure/define gated?) fix is also welcome :)