The ARMC6 compiler inadvertently introduces the `_scanf_mbtowc` symbol
to the build. The commit provides a weak definition of the symbol to
satisfy the linker whenever the symbol is included. This affects ARM
Compiler 6 version 6.12 and earlier.
The compiler error was previously observed when the MICROLIB library is
used with the uARM toolchain. However, the weak definition was put in
`mbed-os/rtos` which is not included when the bare metal profile is used.
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
Hugues Kamba