Use file(INSTALL) to install doxygen documentation.

The previous approach failed if there were to many files for the shell.

[[Imported from SVN: r6964]]

cmake/modules/DuneDoxygen.cmake

@@ -74,10 +74,11 @@ MACRO (add_doxygen_target)
 
     # When installing call cmake install with the above install target
     install(CODE
-      "execute_process(COMMAND \"${CMAKE_COMMAND}\" --build \"${CMAKE_BINARY_DIR}\" --target doxygen_install_${DUNE_MOD_NAME} )
+      "include(GNUInstallDirs)
        foreach(_file ${doxygenfiles})
          get_filename_component(_basename \${_file} NAME)
-         LIST(APPEND CMAKE_INSTALL_MANIFEST_FILES \${CMAKE_INSTALL_PREFIX}/share/doc/${DUNE_MOD_NAME}/doxygen/\${_basename})
-       endforeach(_file in \${doxygenfiles})")
+         LIST(APPEND CMAKE_INSTALL_MANIFEST_FILES \${CMAKE_INSTALL_DOCDIR}/doxygen/\${_basename})
+       endforeach(_file in \${doxygenfiles})
+       file(INSTALL ${doxygenfiles} DESTINATION \${CMAKE_INSTALL_DOCDIR}/doxygen)")
   endif(DOXYGEN_FOUND)
 ENDMACRO (add_doxygen_target)