qv_thread_scope_split_* first implementation

[GuillaumeMercier]

First draft of implementation for qv_thread_scope_split_*.

Several questions/issues to discuss:

1. both routines do not use the context parameter? Is this an error on my side or should the interface be modified?
2. I question the behavior of the qv_thread_scope_split routine. This version is passing my simple test but I'm unsure that the result is what we want to achieve. To be discussed.
3. The thread bug with two threads being mapped to the same resources has still to be addressed.

[samuelkgutierrez]

Thank you, @GuillaumeMercier! I'll take a closer look at this and merge into master when appropriate. We will address the issues you bring up.

[GuillaumeMercier]

It isn't much, but allows us to further make tests. We'll discuss this next week if possible. I'll try to improve things until then.

[samuelkgutierrez]

Looking good so far. I'm going to bring these changes into master soon. Once I've done that, please continue your work off of master to avoid diverging too much. Thank you.

[GuillaumeMercier]

I'll get rid of the thread-bug-work branch and create a new one from master to continue the work.

[GuillaumeMercier]

Btw, the function names have not been thoroughly thought. Change what you dislike.

[samuelkgutierrez]

@GuillaumeMercier #179 is in. You can start working off master now.