server: Support sending process and thread security descriptors for the "new_process" request in the protocol.
server: implement passing a process security descriptor to CreateProcess.

For now the function "NTDLL_create_struct_sd" has been duplicated in
kernel32.
This is needed because kernel32 makes the server call. kernel32 currently
makes the server call because NtCreateProcess(Ex) has not been implemented in
ntdll. When NtCreateProcessEx (and NtCreateThreadEx) gets implemented, the
server call will be made from within ntdll instead, and this extra function
in kernel32 will no longer be needed.
server: implement passing a thread security descriptor to CreateProcess