Implement postfix incr/decr for local fields
First pass on for loop codegen
Fix issue affecting for loops with empty initializers
It didn't handle EmptyExpr
Throw more useful exception when the Bad Thing happens
Implement string constants
Fix assign right hand sides causing "pop on empty stack"
Right-hand sides of assignment expressions generated istore instructions due to "being in assignment expressions"
Fix an issue where for loop tests were never output
Finish for4.j