ansi: remove obsolete code/files for de-ANSI-fication support

ansi: remove obsolete code/files for de-ANSI-fication support

* lib/ansi2knr.1, lib/ansi2knr.c: Deleted.
* lib/Makefile.am (dist_pkgvdata_DATA): Do not list them anymore.
* lib/am/ansi2knr.am: Delete.
* lib/am/Makefile.am (dist_am_DATA): Do not list it anymore.
* lib/Automake/Variable.pm (%_am_macro_for_var): Remove entries for
`ANSI2KNR' and `U'.
* m4/depout.m4 (_AM_OUTPUT_DEPENDENCY_COMMANDS): Don't care anymore
about possible definition of the `$U' variable.
* automake.in (@common_files): Drop `ansi2knr.1' and `ansi2knr.c'.
(struct): Remove scalar field `ansi'.
All callers adjusted.
(&lang_c_finish, %de_ansi_files): Remove, they're not required
anymore.
All callers adjusted.
($get_object_extension_was_run): Fix typo in comment.
(&get_object_extension): Drop code dealing with de-ansification;
this function basically a no-op now, but is required to properly
initialize `$get_object_extension_was_run' variable.
(&handle_languages, &handle_compile, &lang_c_rewrite): Drop code
dealing with de-ansification.