xgettext: Split source code into smaller files.

xgettext: Split source code into smaller files.

* gettext-tools/src/rc-str-list.h: New file, extracted from
gettext-tools/src/xgettext.h.
* gettext-tools/src/xg-encoding.h: Likewise.
* gettext-tools/src/xg-mixed-string.h: Likewise.
* gettext-tools/src/xg-arglist-context.h: Likewise.
* gettext-tools/src/xg-arglist-callshape.h: Likewise.
* gettext-tools/src/xg-arglist-parser.h: Likewise.
* gettext-tools/src/xg-message.h: Likewise.
* gettext-tools/src/xg-encoding.c: New file, extracted from
gettext-tools/src/xgettext.c.
* gettext-tools/src/xg-mixed-string.c: Likewise.
* gettext-tools/src/xg-arglist-context.c: Likewise.
* gettext-tools/src/xg-arglist-callshape.c: Likewise.
* gettext-tools/src/xg-arglist-parser.c: Likewise.
* gettext-tools/src/xg-message.c: Likewise.
* gettext-tools/src/xgettext.h: Remove declarations that moved to rc-str-list.h
and xg-*.h.
(add_all_comments, comment_tag, msgstr_prefix, msgstr_suffix,
default_syntax_check, current_formatstring_parser1,
current_formatstring_parser2, current_formatstring_parser3): New declarations.
(xgettext_comment, xgettext_comment_reset, savable_comment_to_xgettext_comment,
recognize_qt_formatstrings): New declarations.
(substring_match): Remove obsolete declaration.
* gettext-tools/src/xgettext.c: Include xgettext.h first.
Include <iconv.h>, rc-str-list.h, xg-encoding.h, xg-arglist-context.h,
xg-message.h. Don't include xsize.h, po-xerror.h, unistr.h.
(add_all_comments, comment_tag, msgstr_prefix, msgstr_suffix,
default_syntax_check): Make global.
(split_keywordspec, insert_keyword_callshape): Moved to xg-arglist-callshape.c.
(null_context, passthrough_context, inherited_context,
null_context_list_iterator, passthrough_context_circular_list,
passthrough_context_list_iterator, flag_context_list_iterator,
flag_context_list_iterator_advance, flag_context_list_table_lookup): Move to
xg-arglist-context.c.
(flag_context_list_table_insert): Move bulk of body to new function
flag_context_list_table_add in xg-arglist-context.c.
(xgettext_comment, xgettext_comment_reset, savable_comment_to_xgettext_comment):
Make global.
(current_formatstring_parser1, current_formatstring_parser2,
current_formatstring_parser3): Make global.
(non_ascii_error_message, from_current_source_encoding): Move to xg-encoding.c.
(CONVERT_STRING, set_format_flags_from_context, warn_format_string,
remember_a_message, remember_a_message_plural): Move to xg-message.c.
(arglist_parser_alloc, arglist_parser_clone, arglist_parser_remember,
arglist_parser_remember_msgctxt, arglist_parser_decidedp, arglist_parser_done):
Move to xg-arglist-parser.c.
(mixed_string_buffer_alloc, mixed_string_buffer_append_to_curr_buffer,
mixed_string_buffer_grow_utf8_buffer, mixed_string_buffer_append_to_utf8_buffer,
mixed_string_buffer_flush_utf16_surr, mixed_string_buffer_flush_curr_buffer,
mixed_string_buffer_append_char, mixed_string_buffer_append_unicode,
mixed_string_buffer_done): Move to xg-mixed-string.c.
(recognize_qt_formatstrings): New function.
* gettext-tools/src/x-*.h: Include xg-arglist-context.h instead of xgettext.h.
* gettext-tools/src/x-*.c: Update include directives.
* gettext-tools/src/its.h: Likewise.
* gettext-tools/src/Makefile.am (noinst_HEADERS): Add the new .h files.
(xgettext_SOURCES): Add the new .c files.
* gettext-tools/src/FILES: Update.