#3 \"pline\" items not being redrawn correctly

[Sean McKnight]

Re-setting the coordinates of a "pline" item via the "coords" command will give different results on the display, depending
upon how the coordinates were specified.

If given as a single list of four values, the line re-displays correctly:

% .c create pline 0 0 100 100
1
% set crdList {0 0 1000 1000}
% .c coords 1 $crdList
(Line is re-drawn correctly)

If given as four separate coordinates the line is not re-drawn correctly even though
the coordinates have been reset:

% .c create pline 0 0 100 100
1
% .c coords 1 0 0 1000 1000
(Line is not redrawn correctly)

Looks like the bounding box is not being calculated as it should be in "tkCanvPline.c".

[Sean McKnight]

Patch for "pline" redraw problem