xgettext: Avoid a warning 'Charset "CHARSET" is not a portable encoding name'.
* gettext-tools/src/po-charset.h (po_lex_charset_set): Add is_pot_role
parameter.
* gettext-tools/src/po-charset.c (po_lex_charset_set): Likewise.
* gettext-tools/src/po-lex.h (gram_pot_role): New declaration.
(lex_start): Add is_pot_role parameter.
* gettext-tools/src/po-lex.c (gram_pot_role): New variable.
(lex_start): Add is_pot_role parameter.
(lex_end): Update.
* gettext-tools/src/po-gram-gen.y (do_callback_message): Pass gram_pot_role to
po_lex_charset_set.
* gettext-tools/src/read-catalog-abstract.h (struct catalog_input_format): Add
is_pot_role parameter to the 'parse' member.
(catalog_reader_parse): Add is_pot_role parameter.
* gettext-tools/src/read-po.c (po_parse): Add is_pot_role parameter.
* gettext-tools/src/read-properties.c (properties_parse): Likewise.
* gettext-tools/src/read-stringtable.c (stringtable_parse): Likewise.
* gettext-tools/src/read-catalog-abstract.c (catalog_reader_parse): Add
is_pot_role parameter.
* gettext-tools/src/x-po.c (extract): Pass is_pot_role as true.
* gettext-tools/src/xgettext.c (read_exclusion_file): Likewise.
* gettext-tools/src/read-catalog.c (read_catalog_stream): Pass is_pot_role as
false.
* gettext-tools/src/msgfmt.c (read_catalog_file_msgfmt): Likewise.
