gettextize: Remove --intl option.

gettextize: Remove --intl option.

* gettext-tools/misc/gettextize.in (func_usage): Don't mention --intl option.
Signal an error if the --intl option is specified.
Simplify main code accordingly.
* gettext-tools/doc/gettextize.texi: Remove --intl option description.
* gettext-tools/doc/gettext.texi (Prerequisites): Remove mention of intl/
directory.
(configure.ac): Suggest to use AM_GNU_GETTEXT([external]) always. Remove mention
of intl/ directory.
(config.guess): Suggest them always.
(aclocal): Shrink the list of .m4 files.
(acconfig): Remove subsection.
(config.h.in): Remove mention of intl/ directory.
(Makefile, src/Makefile, lib/gettext.h): Likewise.
(AM_GNU_GETTEXT): First argument must be 'external'. Remove third argument.
(AM_GNU_GETTEXT_INTL_SUBDIR): Remove subsection.
(Language Implementors): Remove mention of intl/ directory. Mention that
Solaris 11 gettext works like GNU gettext.
(Maintainers for other Languages): Remove mention of intl/ directory.
* gettext-tools/doc/autopoint.texi: Update explanation of name.
* NEWS: Mention the change.