Add pdz, to auto-seek to end of disassembly

This makes it work a bit like gdb:

    [0x12345678] pd 0x10
    (... disassembled 16 instructions, but position doesn't change)
    [0x12345678] pd 0x20
    (... disassembled 32 at same place, but position doesn't change)
    [0x12345678] pdz 0x10
    (... disassembled 16 instructions, but moved seek to end of disassembly)
    [0x123456b8] pdz 0x20
    (... disassembled 16 instructions, but moved seek to end of disassembly)
    [0x12345738] pdz 0x20

Also same for pDz with bytes