If a header-only library requires linking a 3rd party library, the ..._LIBRARIES variable could not be used in depending projects, because it
contained NOTFOUND.

Removed libtine linking workaround from FindDOOCS. Doocs libraries now are themselves linked correctly against tine.

Automatically adding CMAKE_CXX_STANDARD to all projects is giving too much trouble because different CMAKE versions add different --std=gnu... flags which do not play well the the --std=c++... which we use.

This reverts commit ddb4d575.

The automatic merge process got massively confused

This confused git massively

The pkg-config file is missing so we have to search for the library
manually