Improved handling of value type containers in foreach

[suprstefan]

I spent some time digging into fixing #92. Since I haven't looked that much at the VM and bytecode for angelscript I might be missing something, but it fixes my case and doesn't break any other at least. And the VM looks pretty standard tbh.

To summarize it and my assumptions:

• Reference types are stored as pointers internally as far as the VM is concerned.
• The foreach expressions evaluate the expression to the right of ":" and stores the result in a temporary variable.
• The temporary variable will be a pointer for reference types and the actual value for value types.
• When making the calls to opForX the previous behavior always used asBC_PshVPtr which resulted in a by-value copy of what was in the temporary variable storage. This works great for reference types, since it just copies the pointer, but for value types it creates a garbage "this" pointer.
• To fix this I changed it to instead use asBC_PSF if the container type is a value type, to make it store a pointer to the value as "this".
• Since references can't be used as lvalues I don't think I have to care about them? I assume they're stored as pointers as well.

Does this look correct?

[anjo76]

Thanks a lot for providing this fix. It will save me time to investigate on my own.

I'll do a more detailed review and testing on my own before I merge it, but at a quick glance on what you've done it does look to be correct.