release notes: add warning about 32-bit systems
release notes: add warning about 32-bit systems

dobbscoin/dobbscoin-source,dobbscoin/dobbscoin-source,dobbscoin/dobbscoin-source,dobbscoin/dobbscoin-source,dobbscoin/dobbscoin-source,Earlz/dobbscoin-source,Earlz/dobbscoin-source,Earlz/dobbscoin-source,Earlz/dobbscoin-source,dobbscoin/dobbscoin-source,Earlz/dobbscoin-source,Earlz/dobbscoin-source