Fix sizes of internal controls of AcquireImageControl

A Mono layout bug truncates the size of controls anchored right and
left inside AcquireImageControl.  This provides a workaround to fix
https://jira.sil.org/browse/BL-778 "[Linux] Image Toolbox only
displays 2 columns of AoR images (Windows does 3)".  The bug would
probably affect WeSay as well as Bloom.
Possibly > would be better than !=, but I'm not sure it's a significant difference.  The numbers come from comparing the sizes set for various controls in the .Designer.cs file.  I know that's not entirely satisfactory in case someone edits the control and changes the sizes.  But there's no other way to get the numbers because the original sizes of the controls are not preserved anywhere, so the desired margins associated with the bottom and right anchor points are not preserved anywhere.  (That's the essence of the bug in the Mono code, calculating those margins at the wrong point in time.)