This commit involves the PAE paging itself, refactoring the
vspace code to extra what is common between PAE and 32bit paging,
as well as some renaming to not call the root paging structure
a PD
A C++ compiler will attempt to interpret 'return info' as an invocation of a copy
constructor. Even though the copy constructor is auto-generated (and eventually
completely eliminated due to inlining) and just does obvious member copying it
still results in an intermediate invocation that must take a reference to 'info'.
Because 'info' is a register variable it is not permissable to take a reference
to it. Manually reconstructing a new info from the .words keeps everything as
Plain Old Data
