[fpc-pascal] shift right operation with variables

[Marco van de Voort]

In our previous episode, Peter said:
> I was going to comment that the 'bitmask example doesn't work, which it
> didn?t, but looks like its been recently fixed by adding the needed
> QWord cast on the '1's.
> 
> http://wiki.freepascal.org/Bit_manipulation
> 
> Qwords are certainly trickier to use the Dwords.

Actually dwords had the same problems before the introduction of int64.

Now Qword is the one type without a signed type larger than it.