Ticket #3757: cannot show more than one column in user defined listing mode.
In user-defined listing mode, the format string lets us specify how many
columns to display. E.g., for 3 columns:
"half 3 type name | size | perm"
However, parse_panel_size() reads this digit only when `panel->list_type ==
list_brief`. We remove this check.
Incidentally, the assignment there to `panel->brief_cols` isn't needed. In
list_brief mode, `panel->brief_cols` is already set.
We also fix a related problem in the mouse handler: it erroneously assumes
`panel->list_cols > 1` happens only in list_brief mode.
(These bugs were introduced in commit
fb474bc1c157.)
Signed-off-by: Mooffie <mooffie@gmail.com>