Addendum to commit 0a392b18.
The actual problem that existed all along was that the buffers being
validated with CsrValidateMessageBuffer() were not the correct ones!
What had to be checked is the string buffer **INSIDE** the UNICODE_STRING
structures! Indeed, it is these buffers that we are allocating on client side,
see https://github.com/reactos/reactos/blob/9b421af1/dll/win32/kernel32/client/dosdev.c#L324-L336
Dedicated to Pierre Schweitzer.
This will notably bring support for DOS mapping with LUID devices
(not yet supported in the kernel, though).
This also reduces complexity (and thus memory usage) with the "history"
thing. Multiple targets are stored in the link target as MULTI_SZ string.
This fixes regressions introduced with kernel32 fixes/rewrites.
