patch 1:
- Added variable that will be transfered by cmake into doxygen to be used to test.
- please note that only  ENABLED_SECTIONS variables are visible to doxygen.
- doing "make docs" in legato, will now detect and bring MangOH into the doxygen.

Change-Id: I4e5aeee4ffbfdc541e8fcfba2b6f02f4143e06b3