report_comdat_group for kept comdat sections. * testsuite/Makefile.am (incremental_comdat_test_1): New test. * testsuite/Makefile.in: Regenerate. * testsuite/incr_comdat_test_1.cc: New source file. * testsuite/incr_comdat_test_2_v1.cc: New source file. * testsuite/incr_comdat_test_2_v2.cc: New source file. * testsuite/incr_comdat_test_2_v3.cc: New source file.