* include/grub/ieee1275/ieee1275.h: Introduce flag for firmwares

that hang if GRUB tries to setup colors.
* term/ieee1275/ofconsole.c (grub_ofconsole_init): Don't set
colors for firmwares that don't support it.
* kern/powerpc/ieee1275/cmain.c (grub_ieee1275_set_flag):
Recognize Open Hack'Ware, set flags to work around its
limitations.

include/grub/ieee1275/ieee1275.h

@@ -86,6 +86,9 @@ enum grub_ieee1275_flag
 
   /* OLPC / XO firmware hangs when accessing USB devices.  */
   GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY,
+
+  /* Open Hack'Ware stops when trying to set colors */
+  GRUB_IEEE1275_FLAG_CANNOT_SET_COLORS,
 };
 
 extern int EXPORT_FUNC(grub_ieee1275_test_flag) (enum grub_ieee1275_flag flag);