Consistent ptr typedefs for kd tree flann

[wsascha]

Consistent use of 'Dist' template type for users having custom distance functors.

[SergioRAgostinho]

First look into it looks OK. Two comments:
- Could you please write a test exactly exploiting a custom distance case
- Please squash into a single commit

[SergioRAgostinho]

This should also be modified accordingly.

[taketwo]

If that is modified, then this should also be updated, of course.

[wsascha]

Sorry guys, I completely forgot about this!

I propose to instantiate only with the default Dist template parameter. If anyone needs special distances types, they can instantiate those by themselves.

[SergioRAgostinho]

I propose to instantiate only with the default Dist template parameter. If anyone needs special distances types, they can instantiate those by themselves.

That is, to leave it unchanged? My idea was not to instantiate more types. I just wanted to make it clear when reading the instantiations that the class actually depends on two separate types.

But if the general acceptance is to leave it like, then this one is good to go.

[taketwo]

I agree that we do not need to preinstantiate with other distance types. So far everyone was happy with the default one. (And which ones would you choose anyway?)

As per Sergio's comment, yes, we can update the instantiation macro. But in user code instantiation happens implicitly, so the macro is not really needed.