xgettext: Protect file names with spaces through Unicode U+2068, U+2069.
* gettext-tools/src/pos.h: Include <stdbool.h>.
(pos_filename_has_spaces): New declaration.
* gettext-tools/src/pos.c: New file.
* gettext-tools/src/msgl-ofn.h: New file.
* gettext-tools/src/msgl-ofn.c: New file.
* gettext-tools/src/FILES: Update.
* gettext-tools/src/Makefile.am (noinst_HEADERS): Add msgl-ofn.h.
(COMMON_SOURCE): Add pos.c.
(libgettextsrc_la_SOURCES): Add msgl-ofn.c.
* gettext-tools/libgettextpo/Makefile.am (libgettextpo_la_AUXSOURCES): Likewise.
* gettext-tools/src/write-catalog.h (struct catalog_output_format): Add field
requires_utf8_for_filenames_with_spaces.
* gettext-tools/src/xgettext.c: Include pos.h, msgl-ofn.h.
(finalize_header): Convert the message domain to UTF-8 also when some message
has file names with spaces.
* gettext-tools/src/write-po.h (message_print_comment_filepos): Add charset
parameter.
* gettext-tools/src/write-po.c: Include pos.h.
(message_print_comment_filepos): Add charset parameter. If a file name has
spaces, enclose it in U+2068 and U+2069 characters.
(message_print, message_print_obsolete, output_format_po): Update.
* gettext-tools/src/write-properties.c (write_message,
output_format_properties): Update.
* gettext-tools/src/write-stringtable.c (output_format_stringtable): Update.
* gettext-tools/tests/xgettext-17: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add it.
