Fix a bug resulting in black screen when loading Linux using a
packed video mode.
* kern/i386/pc/startup.S (grub_vbe_bios_getset_dac_palette_width): New
function.
* include/grub/i386/pc/vbe.h (GRUB_VBE_CAPABILITY_DACWIDTH): New macro.
(grub_vbe_bios_getset_dac_palette_width): New function.
(grub_vbe_bios_get_dac_palette_width)
(grub_vbe_bios_set_dac_palette_width): New macros (act as wrappers for
grub_vbe_bios_getset_dac_palette_width()).
* video/i386/pc/vbe.c (grub_vbe_probe): Use `GRUB_VBE_STATUS_OK' to
check for return status.
(grub_vbe_get_video_mode_info): When getting information for a packed
mode (<= 8 bpp), obtain DAC palette width using
grub_vbe_bios_getset_dac_palette_width(), and use that for initializing
{red,green,blue}_mark_size.
f56a875639