Add localization support to com_err.

* Add compile_et arguments --textdomain and --localedir.
* Store text domain and localedir at the end of error tables.
* error_message() calls dgettext if the table has a text domain.
* add_error_table() calls bindtextdomain if the table has a localedir.
* Define N_() as no-op in generated source and mark up error messages.
* When using system compile_et, test for --textdomain support.
* Use --textdomain option when available.
* Run xgettext over generated sources in compile_et rule.
* Translate com_err results in krb5int_get_error() if com_err won't.

https://github.com/krb5/krb5/commit/cb8b1138d6e349a77507f3c561fc7ee2dde5cd7c
Commit By: ghudson
Revision: 24960
Changed Files:
U   trunk/src/aclocal.m4
U   trunk/src/config/post.in
U   trunk/src/config/pre.in
U   trunk/src/po/Makefile.in
U   trunk/src/po/mit-krb5.pot
U   trunk/src/util/Makefile.in
U   trunk/src/util/et/compile_et.1
U   trunk/src/util/et/compile_et.sh
U   trunk/src/util/et/error_message.c
U   trunk/src/util/et/et_c.awk
U   trunk/src/util/gss-kernel-lib/Makefile.in
U   trunk/src/util/support/errors.c