core: Add support for creating page tables with hugepages

core: Add support for creating page tables with hugepages

When adding support for generating hugepages during page_map_create, we
also need to address the issue of overwriting or splitting up such
pages. When partially unmapping a hugepage, we need to break it up
first, then unmap the included pages. This break-up may fail when we are
short on memory, thus page_map_destroy may actually fail now, and we
have to take this into account on the caller side.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>