Modula-2 support: Add Modula-2 support in the tools.

Modula-2 support: Add Modula-2 support in the tools.

* gettext-tools/doc/lang-modula2.texi: New file.
* gettext-tools/doc/Makefile.am (gettext_TEXINFOS): Add it.
* gettext-tools/doc/gettext.texi (PO Files): Mention modula2-format.
(No string concatenation): Mention string concatenation in Modula-2.
(Translators for other Languages): New subsection "Modula-2 Format Strings".
(List of Programming Languages): Include lang-modula2.texi.
* gettext-tools/doc/xgettext.texi: Document the -L Modula-2 option.
* gettext-tools/src/message.h (format_modula2): New enum value.
(NFORMATS): Increment.
* gettext-tools/src/message.c (format_language, format_language_pretty): Add an
entry for format_modula2.
* gettext-tools/src/format-modula2.c: New file.
* gettext-tools/src/format.h (formatstring_modula2): New declaration.
* gettext-tools/src/format.c (formatstring_parsers): Add formatstring_modula2.
* gettext-tools/src/x-modula2.h: New file.
* gettext-tools/src/x-modula2.c: New file.
* gettext-tools/src/xgettext.c: Include x-modula2.h.
(flag_table_modula2): New variable.
(main): Invoke init_flag_table_modula2, x_modula2_extract_all,
x_modula2_keyword.
(usage): Document the -L Modula-2 option.
(xgettext_record_flag): Support format_modula2.
(language_to_extractor, extension_to_language): Support Modula-2.
* gettext-tools/src/FILES: Mention format-modula2.c, x-modula2.h, x-modula2.c.
* gettext-tools/src/Makefile.am (noinst_HEADERS): Add x-modula2.h.
(FORMAT_SOURCE): Add format-modula2.c.
(xgettext_SOURCES): Add x-modula2.c.
* gettext-tools/libgettextpo/Makefile.am (libgettextpo_la_AUXSOURCES): Add
format-modula2.c.
* gettext-tools/po/POTFILES.in: Add src/format-modula2.c, src/x-modula2.c.
* gettext-tools/woe32dll/gettextsrc-exports.c: Export formatstring_modula2.
* gettext-tools/tests/format-modula2-1: New file.
* gettext-tools/tests/format-modula2-2: New file.
* gettext-tools/tests/xgettext-modula2-1: New file.
* gettext-tools/tests/xgettext-modula2-2: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add the new tests.
* NEWS: Mention the Modula-2 support.