* coin3d 4.0.0 default location is /usr/share/doc/Coin/html/
* misuses of find_files() if several candidates for filename
* export variable COIN3D_DOC_FOUND that is used by cMake/FreeCAD_Helpers/PrintFinalReport.cmake
Currently cmake looks for coin.tag and coin.tag.gz when searching a
tag file of the Coin3D documentation. On some coin3d installations,
the tag file is named Coin.tag or Coin.tag.gz. This patch improves
the search by adding additional hints to the find_file() test for
the tag file.
