This patch changes `EmitPPCBuiltinExpr` in `CGBuiltin.cpp` to remove
the loop at the beginning of the function that emits the arguments and
to delay emitting the arguments until inside the switch statement. These
changes will put `EmitPPCBuiltinExpr` in line with the strategy of the
target independent function `EmitBuiltinExpr`. Also, this patch
ensures that arguments are only emitted once.
Tests that included builtins affected by these changes have been modified
to match expected behaviour.