[BASESRV] Rewrite DOS devices management

[BASESRV] Rewrite DOS devices management

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.