FindDoxygen: Optionally use custom doxygen binaries path
The change to cover issue #24860 (closed) : In our windows build environment, we use doxygen not as installation but as binaries in custom relative folder. And currently it's impossible to make FindDoxygen work for us - "_Doxygen_find_doxygen" macro start to work at the moment of include and searches in predefined folders and registry. And currently there is no way to make this find doxygen binaries.
This change takes into account new variable CMAKE_DOXYGEN_PATH
and uses it to find doxygen binaries
Currently i'm not sure in what line i have to add the doc, please advice