initial commit of nt64/bits; these header files should be kept in sync
    with their linux x86_64 counterparts, with three minor exceptions:
    
    1) page size (65536)
    2) jmp_buf (10 pointers)
    3) TIOCGPTN and TIOCSPTLCK (normal sequence)
    
    signed-off by Z. Gilboa; see copying.midipix (9cd0746c) for additional information.