Clean up/refine two XTREE issues related to the protection of individual cells in an otherwise editable column. (The technique for this, which hasn't changed, is to put a "|" in the first column of the cell's entry in the answer array.) One problem now fixed is that XTREE was sometimes ignoring the "|" indicator on the initial data load if the first 500 bytes of the answer array were all blank. A second issue, more of a limitation than a problem, was that the mechanism didn't allow any data to be displayed in such cells. Now, the remainder of the cell's entry in the data array (following the "|" in the first byte) will be used to load and update the cell.
Note that if the column also allows a color byte, the color byte comes before the "|".
