A few documentation typos in doxgen automatic links and release of threads

[anotheruserofchibios]

Hi,

I spotted a few typos in the documentation:

• "Initializes s @p" -> "Initializes a @p"
• @p bsem -> @p chBSem
• @p chthd -> @p chThd
• @p threads.h -> @p chschd.h
• how to release dynamic threads and when they are removed from registry

Please find attached a single patch file containing multiple commits (one for each of the above points).

I'm not so sure about the last point but I think the documentation was not consistent everywhere. It may still be improved of course.

Kind regards,

[Giovanni]

Thanks, typo fixes are never enough

Giovanni