Contributions from:
- Gustavo Jose de Sousa <gustavo.sousa@intel.com>
- José Roberto de Souza <jose.souza@intel.com>
- Lucas De Marchi <lucas.demarchi@intel.com>
- Patrick J.P <patrick.pereira@intel.com>
This centralized namespace header encourages centralizing things on
umbrella headers that are a pain to maintain. Force each part of
AP_HAL_Linux to include what is used.
While at it, do some whitespace cleanups and minor changes to adhere to
coding style.