[PATCH] updated chapter references in chapter 2 of c-user doc.

[Chris Johns]

> On 18 May 2018, at 6:11 pm, Sebastian Huber <sebastian.huber at embedded-brains.de> wrote:
> 
> This stuff in
> 
> https://docs.rtems.org/branches/master/c-user/overview.html#manual-organization
> 
> looks hard to maintain.

I have not had a chance to see if this can be automated. 

> What is the value for the user? There are no real links in this section.

I think this section could be less specific, the chapter details are not needed, and more generic about the sections of interest, for example configuration, errors, SMP, scheduling, etc. 

Chris