Fix issue effecting assignment expressions
Assignment expressions were emitting the left-hand side first, followed by the right-hand side, which (as everyone knows) is the Wrong Thing. This resulted in the top of the stack being stored in a variable before the value in the assignment statement was on the stack, resulting "pop on empty stack" errors when the stack is empty, and the wrong value being stored when something was on the stack.

Correct bytecode is now generated for lab4-samples/if5.decaf; meaning that the if-statement chain is now finished.