it seems that doxygen 1.18.13 is not behaving the same as 1.1811 (Travis one).
one might need to remove some spaces in the signature as they are different depending on Doxygen's version
All user settings/plugins, etc are now loaded from APPDATA for each
platform and no longer .qgis3 and are isolated from each other.
This allows for different profiles depending on what the user of QGIS
needs, e.g test, prod, demo, etc
Profile menu allows for switching between profiles, or creating new
ones.
instead of adding an extra CMakeLists in .ci/travis/code_layout to build API doc, astyle and run tests (indentation, spelling, sip, doc coverage), the top CMakeLists has been adapted to allow not building core libraries and possibly just the static code layout
* astyle has been moved from /src/astyle to /lib/astyle (I would propose to move all external libraries, and possibly add git submodules)
