libgettextpo: Remove static variable 'width.0'.
* gnulib-local/lib/xerror.h: Include <stddef.h>.
(multiline_warning, multiline_error): Change return type to size_t. Don't
suggest to pass a NULL prefix.
(multiline_append): New declaration.
* gnulib-local/lib/xerror.c (multiline_internal): New function, extracted from
multiline_warning.
(multiline_warning, multiline_error): Reject a NULL prefix. Call
multiline_internal.
(multiline_append): New function.
* gettext-tools/src/msgl-charset.c (compare_po_locale_charsets): Invoke
multiline_append instead of multiline_warning with NULL argument.
* gettext-tools/src/msgfmt.c (msgfmt_parse_debrief): Invoke multiline_append
instead of multiline_error with NULL argument.
* gettext-tools/src/po-error.c (void_multiline_warning, void_multiline_error):
New functions.
(po_multiline_warning, po_multiline_error): Use them as initializer.
* gettext-tools/libgettextpo/gettext-po.c (void_multiline_warning,
void_multiline_error): New functions.
(po_file_read_v2, po_file_write): Use them as defaults for po_multiline_warning,
po_multiline_error.
