16 bit xorshift rng in intel assembly

As described in George Marsaglia's paper located here. Marsaglia doesn't look at 8 or 16 bit, but there's more information here from cjh.

After some runs through diehard, these triplets were the only ones to not fail spectacularly:

• 4,3,7
  
• 5,11,6
  
• 5,9,8
  

I didn't have an assembler handy, debug will do:

1791:0200 51            PUSH    CX
1791:0201 52            PUSH    DX
1791:0202 B80100        MOV     AX,0001
1791:0205 89C2          MOV     DX,AX
1791:0207 B103          MOV     CL,03
1791:0209 D3E0          SHL     AX,CL
1791:020B 31C2          XOR     DX,AX
1791:020D 89D0          MOV     AX,DX
1791:020F B105          MOV     CL,05
1791:0211 D3E8          SHR     AX,CL
1791:0213 31C2          XOR     DX,AX
1791:0215 89D0          MOV     AX,DX
1791:0217 B10B          MOV     CL,0B
1791:0219 D3E0          SHL     AX,CL
1791:021B 31C2          XOR     DX,AX
1791:021D 92            XCHG    DX,AX
1791:021E 2E            CS:
1791:021F A30302        MOV     [0203],AX
1791:0222 5A            POP     DX
1791:0223 59            POP     CX
1791:0224 C3            RET