Added auxiliary function for setting width and height of region of a rectangular sheet.
Added auxiliary function for setting width and height of region of
a rectangular sheet.

Modified layout panes to use auxiliary function so as to avoid setting
upper-left corner of region.  This makes the panes scroller-friendly.

Removed method on allocate-space for gereral composite pane.

Added method on allocate-space for top-level-sheet-pane.

quek/mcclim,informatimago/mcclim,informatimago/mcclim,quek/mcclim