Fix BL-651 "[Linux] Calendar setup ... entry boxes are mis-registered"

There doesn't seem to be any way to get identical output on
1) Windows 7, 2) Linux X display, and 3) Linux xephyr display.
This change seems to be about the best compromise, showing minimal
change on Windows 7 and acceptable display on Linux.
Merge pull request #202 from StephenMcConnel/Fix-BL-651

Fix BL-651 "[Linux] Calendar setup ... entry boxes are mis-registered"