'Spelt' is the traditional British form but it's not recognised in most other parts of the world. (i.e. it's not part of 'international english').
'Spelled' is creeping in from the US and seems to be the accepted form for many British newspapers.
According to the OED, irrespective of the form chosen, the correct way of pronouncing the word is 'spelt'. This is unusual because it's normally the US form of a word which matches spelling with pronunciation; here it's the British form which does so.
Yes, the old use has died out. And it's not the only example. I use 'learnt' but 'learned' is used nowadays. I used to think of the word said 'learn-ed' as someone who had a wide knowledge - e.g. 'the learn-ed professor gave his views'.