Fix warnings from doxygen
../src/core/file/gfal_file_api.h:713: warning: end of file while inside a group ../src/core/common/gfal_config.h:333: warning: end of file while inside a group
../src/core/file/gfal_file_api.h:713: warning: end of file while inside a group ../src/core/common/gfal_config.h:333: warning: end of file while inside a group