Doxygen fails when build for debug 

QSSTV 9.5.11

Building for debug, from src/build:

`qmake CONFIG+=debug ..`

Project MESSAGE: Compiling for x86
Project MESSAGE: dox will be generated

doxygen fails because searches for "documentation" folder in src, while it is in the parent/project root folder. As temporary workaround, "documentation" folder can be moved in "src".



