nlvm update - llvm 13.0.0

[arnetheduck]

<https://github.com/arnetheduck/nlvm/blob/c841f65f979e9bbe81862082d7e896dc4ef6d7ac/llvm/llvm/Core.nim#L40>
 and 
<https://github.com/arnetheduck/nlvm/blob/c841f65f979e9bbe81862082d7e896dc4ef6d7ac/llvm/llvm/Core.nim#L272>
 are two simple examples