Fix bug in sending cores command to engine

Fix bug in sending cores command to engine

The cores command was alwas sent to the engine(s) when the user changed
it through the menu, even when the engine had sent feature smp=0 (which
is default anyway). NewSettingEvent() was patched to send the new
setting conditionally, based on the engine properties as recorded in
ChessProgramStates first, second; In this particular case it now
consults cps->maxCores. (Note the code for testing the second engine
contains some dirty pointer arithmetic.)