Effective address calculation and load/store instruction semantics fi…

…xes.

The 'address' variable in the semantics for load/store instructions should not directly call Dispatcher::read(), but should only store the address of the target location in memory. The semantics have been updated to reflect this. A new method - DispatcherARM64::effectiveAddress() - is added which is called in the above scenario.

In addition, the pre-fix part of the address calculation doesn't have to be performed again in dataflow API since the required information is already encoded in the AST by instruction API.