This fixes a (minor) problem discovered by AMK when you don't want any

This fixes a (minor) problem discovered by AMK when you don't want any
special markup for the first column of a table using {tableii} or {tableiii}.
In LaTeX, this requires using "textrm" as the formatting function, and this
is needed to remove the bogus "<textrm>" that gets generated otherwise.
There should probably be a more general mapping of specified markup to useful
markup, but that doesn't appear needed at the moment.

do_env_tableii(), do_env_tableiii():  If the markup for the first column is
	\textrm, make it empty.

do_cmd_lineii(), do_cmd_lineiii():  If the markup for the first column is
	empty, don't add markup around the text.