* add new API, page::text_list(int opt_flag). The old one
taking no argument is kept for ABI compatibility.
The opt_flag is a bitmask-multiple of the new enum,
page::text_list_option_enum.

* text_box.m_data->text_box_font is an unique pointer to
the storage (if text_list() requests the font info), or
just a null pointer (if text_list() does not request the
font info).

* new option "--show-text-list-with-font" showing font
info, to tests/poppler-dump.cpp. "--show-text-list"
does not load the font info at all.

Co-authored-by: Adam Reichold <adam.reichold@t-online.de>
Co-authored-by: Albert Astals Cid <aacid@kde.org>