htmlext: program options: fix positional_options_description going out of scope (command_line_parser stores a reference; does not copy)
htmlext: program options: fix positional_options_description going out of scope (command_line_parser stores a reference; does not copy)

thomastrapp/hext,thomastrapp/hext,thomastrapp/hext,thomastrapp/hext,thomastrapp/hext,thomastrapp/hext,thomastrapp/hext,thomastrapp/hext