fix for secondary screen
more fixes
more fixes
Factor the code to copy a line into a method.
Add shade operator to rxvt_img.
When rendering the cursor, modify also the rendition of the filler chars
that belong to the char in the cursor cell.

This fixes a rendering bug that occurs if the character in the cursor
cell has width > 1 and both it and the character to the right have the
careful bit set and the same rendition. Bug reported by Tiago Resende.