This allows us to remove the allocFn argument from the vmm functions
which causes the compiler's escape analysis to sometimes incorectly flag
it as escaping to the heap.
The API provides the Map() and MapTemporary() functions that establish
virtual -> physical address mappings using the currently active page
directory table.
Mapped pages can be unmapped using the Unmap() function. When unmapping
virtual addresses, the page tables leading to them will not be
automatically released even if they are empty. This will be addressed by
a future commit.
