For the TimestampsToReturn and BrowseDirection enums
we have status codes for invalid values.

OpcUa_BadTimestampsToReturnInvalid
OpcUa_BadBrowseDirectionInvalid

But there is no invalid value in the enum, all allowed
values are in fact valid. The CTT needs to check
that these status codes are generated, but to do that
it is necessary to cast some random value to the enum
which causes itself an undefined behaviuor by the rules of C/C++.

Please add a value OpcUa_TimestampsToReturn_Invalid
and OpcUa_BrowseDirection_Invalid to the enum.