Compensate for scrollbar width across all asterisked columns instead of just the last one

[steverice]

When calculating widths for columns with asterisks, the existing code checks to see if the column under consideration is the last column in the grid. If so and the vertical scroll bar is being shown it will reduce that column's width so that it does not cause horizontal overflow.

This pull request shifts the compensation to all asterisked columns, which both reduces the effect on any single column (if there are more than one) and allows the compensation to happen if there is a fixed- or percentage-width column at the rightmost end of the grid, given that there are asterisked columns elsewhere in the grid.