Fix the default palette of PCL simple color mode KCMY (ESC * r -4 U).

set_default_entries() only filled the first 8 of the 16 KCMY palette entries
and set the rest to black, so every raster pixel with the Y plane set printed
black (red, green and yellow areas came out black). This affects PCL 3 colour
jobs from DeskJet-class drivers, e.g. CUPS rastertohp (HP DeskJet Series PPD,
default CMYK) and Ghostscript's cdj550 device.

Filling all 16 entries exposed an off-by-one write in
set_dev_specific_default_palette(): for palettes of more than 8 entries it
also wrote one byte past the current entry, which for the last entry is one
byte past the end of the palette (heap corruption; the reason the upstream
comment says cnt = 15 overruns the palette). That byte was always overwritten
by the next entry, so the write is removed.

--- a/pcl/pcl/pcindxed.c
+++ b/pcl/pcl/pcindxed.c
@@ -287,8 +287,6 @@
         palette[3 * i] = cmy_default[3 * porder[i]];
         palette[3 * i + 1] = cmy_default[3 * porder[i] + 1];
         palette[3 * i + 2] = cmy_default[3 * porder[i] + 2];
-        if (num > 8)
-            palette[3 * i + 3] = cmy_default[3 * porder[i] + 3];
     }
 }
 
@@ -508,6 +506,10 @@
          cnt = 15;
          */
         porder = cmy_order_4;
+        /* cmy_order_4 defines 16 entries (K plane = bit 0, Y plane = bit 3).
+         * Limiting cnt to 8 turned every pixel with the Y plane set black.
+         * cnt never exceeds num, the number of palette entries. */
+        cnt = (num + start > 16 ? 16 - start : num);
     }
     /* set the default colors for up to the first 16 entries */
     set_default_palette[(int)type] (pindexed->pbase,