#2 fix for 621285

[Ryan Hicks]

Instantiation of 'MCScrolledListBox' raises a ValueError
exception in PmwBase: "Component "vertscrollbar" already
exists"

I believe this error is due to the fact that
'MCScrolledListBox' derives from 'Pmw.ScrolledFrame'
which already creates a component with the key
'vertscrollbar'. Therefore, when 'createcomponent' in
PmwBase checks to make sure that the there isn't
already a component with the same key (line 461) the
exception is raised.

I corrected this by changing all occurences of
'vertscrollbar' in MCScrolledListBox (lines 132 and 198) to
'mcslbvertscrollbar'.

[Ryan Hicks]

slightly modified Multiple Column Scrolled ListBox file