Fix file-name recognition in 'etags'

Fix file-name recognition in 'etags'

* lib-src/etags.c (get_language_from_filename): If FILE includes a
leading directory, compare only its basename to the known file
names in lang_names[].

* test/etags/Makefile (RBSRC): Adapt to recent test1.ruby
renaming.
* test/etags/ETAGS.good_1:
* test/etags/ETAGS.good_2:
* test/etags/ETAGS.good_3:
* test/etags/ETAGS.good_4:
* test/etags/ETAGS.good_5:
* test/etags/ETAGS.good_6:
* test/etags/CTAGS.good: Adapt to changes in Ruby file names and
to the results in Makefile due to the above etags.c fix.