Add missing inline attributes to avoid linker issues.

[plietar]

The xoshiro<2>::do_jump specializations need some inline attribute, otherwise including dqrng from multiple compilation units causes linker errors due to symbols being defined multiple times.

While compiling against the latest pre-release, I hit some build errors which this should fix.

Firstly, the dqrng_types.h file was including Rcpp/Lightest, which should provide a slimmer interface to Rcpp. Unfortunately, the decision to include that file is "infectious" and impacts any compilation unit which includes dqrng. This is because including Rcpp/Lightest ends up defining Rcpp_hpp, and subsequent includes of Rcpp.h do nothing. My end applipcation was unable to use Rcpp's extended API because of this.

[rstub]

Thank you for your contribution. I can understand the second point. Sorry for the oversight! I am not so sure about the first point, though? Can you provide a minimal example that shows the issue? Wouldn't it be sufficient if you included Rccp.h before you include any dqrng related header? The latter point should probably be documented.

[plietar]

Wouldn't it be sufficient if you included Rccp.h before you include any dqrng related header?

Yes you're right. I don't know how I hadn't thought of this. Thanks!
I've changed the PR to only add the inline attributes.

The latter point should probably be documented

Let me know if/where you would want me to add something. Maybe we can raise this with Rcpp as well so they can provide guidance that can then be linked to from this repo.

[rstub]

I think I have found an even simpler solution: It is enough for dqrng to include Rcpp/XPtr.h instead of Rcpp/Lightest. Can you test if that works in your use-case independent of the include order?

[plietar]

Yes, that works for me as well, regardless of how I order my includes.

[rstub]

Thanks a lot @plietar!