From the file chainparams.cpp...

Litecoin:

genesis.vtx.push_back(txNew);

Bitcoin:

genesis.vtx.push_back(MakeTransactionRef(std::move(txNew)));

What is this function MakeTransactionRef()?

What is the function std::move()?

Why does Bitcoin have them while Litecoin does not?

Can they be safely be ignored in a new altcoin?

More of the salient differences are highlighted here.