This reverts commit 3c20c24ac0.
Rebirth no longer contains the Descent memory manager, but Rebirth still
has many traces of the paging support used in the DOS version. One of
the unfortunate and subtle traces of this support is that it allocates a
contiguous buffer for game data and loads many of the games bitmaps into
that buffer. The buffer is large enough for most workloads, but not
all. When the buffer is too small, it is discarded by
piggy_bitmap_page_out_all and rebuilt piecemeal to contain only what it
needs. Fixing this would be nice, but the memory ownership rules are
messy. The performance consequences of the legacy approach are not
sufficient to justify the effort to fix this properly. Instead, revert
to the legacy design.
b43dcc1a52