crypt32: Remove iTunes chain from certificate policy tests, there's no guarantee the root cert is trusted.

advapi32: Fix the ACCESS_SYSTEM_SECURITY test by impersonating the token during the call to RtlAdjustPrivileges.

server: Make create_mapping use struct object_attributes and set the security descriptor of file mapping objects.

server: Make create_mutex use struct object_attributes and set the security descriptor of mutex objects.

server: Make create_semaphore use struct object_attributes and set the security descriptor of semaphore objects.

iphlpapi: For platforms that do not implement /proc, return Unimplemented for the functions trying to read from there.