Special rendering methods for removing mouse cursors cannot be removed
like I hoped, since they are needed for removing parts over the border.
Continue fixing bugs in them.

In the vga planar mode renderer, remove removal of the part of the
image over the text window. This was hard-coded for nearly 8x16 fonts
and in practice didn't remove enough for 8x8 fonts. This used the
wrong attribute over cutmarked regions. The caller refreshes with the
correct attribute later, so the attribute bug only caused flicker.
The caller uses the same hard-coding, so the refreshes fix up all the
spots with the wrong attribute, but keep missing the missed spots.
This still gives trails of bits of cursors for cursor motions in the
affected configurations (mainly depth 4 modes with 8x8) fonts. 8x14
fonts barely escape the problem since although the cursor is drawn
as 16x16, its active part is only 9x13 and the active part fits in
the hard-coded 2x2 character cell window for 8x14 fonts. 8x8 fonts
need a 2x3 window.

In the fb non-sparc64 renderer, the buggy image removal was buggier
and was already avoided by returning before it. Remove it completely
and fix nearby style bugs. It was essentially the same as for the vga
planar mode renderer (obfuscated by swapping x and y). This was buggier
since fb should handle more types of hardware so the hard-coding is
wronger.

The remaining fb image removal is also buggier. It never supported
software cursors drawn into the border, and the hardware cursor is
probably broken by other bugs to be fixed soon.