Use correctly-typed external definition for the crash data region, and
eliminate unnecessary pointer indirection.
Results in a small ROM saving even with crash capture disabled, as there
was a pointer for the fault context store in either case. The pointer
isn't needed, as the context store location is fixed according to the
configuration flag.
* Change Doxygen groups structure, splitting first by Public/Internal
This commit also does the following:
* groups the documentation of related API
* moves `events/internal/equeue.h` to `events/equeue.h`
* merges `events/source/README.md` to `events/README.md`
Also includes:
* rename `mbed_sleep_manager.c` to `mbed_power_mgmt.c` to match its
header file
* create Doxygen groups for public and internal APIs
* use relative path to include header files where inconsistent
* update references to internal APIs throughout libraries
* update the copyright year for all modified files