add May 2004 trunk patch to the branch

add May 2004 trunk patch to the branch

Bug Report:
>> Status of the doppelganger (neutral): Level 13 HP 1433(1433) AC 5.
>> [See the HPs!! ]

Michael:
> I used a debugger and traced this massive hit point growth
> to this line in mon.c, function newcham(). (I watched the mhp
> jump from 58 to 567 with this one calculation!
>> Ah, I see that this problem is fixed in the trunk but still present in
>> the branch. This seems serious/abusive enough to warrant the fix to be
>> applied to the branch too, doesn't it?

Pat:
>      I don't think it's all that important but you're welcome to
> extract and adapt the patch if you like.