Debugger info widget should consider the call type at the callsite in addition to the function type

[xusheng6]

Right now the debugger info widget displays info for the call using the info from the function itself. This is good in many cases, but it is not perfect, since:

1. The call can be a function pointer or data variable, which means it does not have the associated function type
2. The call type could have been overridden
3. For variadic functions, e.g., printf, the type at the call site could be more accurate