HPE Adapt (1 of at least 4) - Non-native huge page support

[andyw-lala]

HPE is planning to work with the community to enhance this xpmem repo, to provide the functionality currently supported by our in-house COS-only version. This issue is number 1 in a series of at least 4, and seeks to identify the known issues that must be addressed.

Use conditional compilation to allow support of non-native huge pages, when built for a kernel that supports this feature (e.g., COS)