This function converts a pointer that is mapped to a process into an unmapped pointer.
A mapped pointer is a pointer that is mapped to a specific process's address. For example, if process A is loaded at address 0x0E000000, then an unmapped pointer 0x00011234 in process A points to the same physical location as its mapped version, which is 0x0E011234.
The CeZeroPointer function calls into the ZeroPtr macro. For information about the ZeroPtr macro, see %_WINCEROOT%\Public\Common\OAK\Inc\Pkfuncs.h.