package kit: some fixes for multi-version support

* Use enums/constants/functions instead of preprocessor macros.
* Missing include in PackageInfoAttributeValue.h.
* PackageReaderImpl::Init(): Check version before header size and
return B_MISMATCHED_VALUES instead of B_BAD_DATA, if the version
doesn't match. This allows callers to determine the condition and
try a reader for a different version. A more flexible interface for
that case would be nice, but since we want to support the old package
version only temporarily, the current solution should be good enough.

package kit: some fixes for multi-version support

* Use enums/constants/functions instead of preprocessor macros.
* Missing include in PackageInfoAttributeValue.h.
* PackageReaderImpl::Init(): Check version before header size and
return B_MISMATCHED_VALUES instead of B_BAD_DATA, if the version
doesn't match. This allows callers to determine the condition and
try a reader for a different version. A more flexible interface for
that case would be nice, but since we want to support the old package
version only temporarily, the current solution should be good enough.