Fixed bug with large file viewing
Fixed bug with large file viewing

When viewing a very large file (many gigabytes of data), setCursorPos
calls sometimes fail to ensure that the cursor is visible due to
overflows in the _cursorY variable.  Increasing _cursorY to a 64-bit int
fixes the problem.

parallaxinc/QHexEdit,parallaxinc/QHexEdit,Dax89/QHexEdit