Handle addition in multiple argument form

[zenna]

Handle multiple arguments like :+(%2, %3, %4, %5) (all with potentially different types)

[zenna]

Might be easiest to handle this at the IR level, simply transform

%1 = %2 + %3 + %4

into

%1a = %2 + %3
%1 = %1a + %4

Might need to be careful about non-associativity of floating point operators