Member function increases size of a struct defined in a function - is this a bug?

[Ferdinand Majerech]

Ran into this while playing around with std.bitmanip.bitfields 
for packet protocol fields.

```
void fun()
{
     struct InnerFun
     {
         ubyte a;
         void fun() {}
     }
     struct InnerNoFun
     {
         ubyte a;
     }
     pragma(msg, "InnerFun ",   InnerFun.sizeof);  // prints 16
     pragma(msg, "InnerNoFun ", InnerNoFun.sizeof); // prints 1
}
```

Size of InnerFun is 16 while size of InnerNoFun is 1 - this took 
a while to debug as I could not figure out why my protocol 
headers are unexpectedly large - `align(1)` did not help.

This does not happen if the structs are defined outside of a 
function.

Is this the result of some D feature?
I can imagine this could happen if InnerFun had a silently added 
context pointer, but I don't know of such a feature in D.


Reported here:
https://issues.dlang.org/show_bug.cgi?id=20564
remove if this is expected behavior.