Variable declaration was also causing this issue.
It was caused by a value being left on the stack after these statements.
It wasn't a quick fix, as chained assignments depended on it. Now, the
assignment opcode has a configuration option, indicating if the last
value should be left on the stack or not.
This also means the benchmark in 'scripts/benchpress.toy' will no longer
cause a stack overflow.
Fixed#171
Kayne Ruse
9141102f2e