vm_space no longer relies on page_manager to map pages during a page
fault. Other changes that come with this commit:
- C++ standard has been changed to C++17
- enum bitfield operators became constexpr
- enum bifrield operators can take a mix of ints and enum arguments
- added page table flags enum instead of relying on ints
- remove page_table::unmap_table and page_table::unmap_pages
Justin C. Miller
1b392a0551