HEADS UP: Framebuffer console support on x86

["Jared D. McNeill" <jmcneill%invisible.ca@localhost>]

Hey folks --

I have added support to the x86 bootloader for VESA BIOS extensions. 
With a new bootloader and -current kernel that includes genfb(4) you can 
now select between VGA text and raster console modes in biosboot on both 
i386 and amd64. This functionality obsoletes vesafb(4) which is i386-only.

VBE modes are configured with the new 'vesa' command. Usage, when present:

    * vesa {modenum|modestr}
      Enable specific VBE mode. The mode can be specified either as a
      VBE mode number (eg. 0x101) or as a string (eg. 800x600x16).
    * vesa {enabled|disabled}
      Enable / disable linear framebuffer, default mode is 640x480x8.
      May be changed in the future to determine mode based on VBE/DDC
      where available.
    * vesa list
      List modes supported by the firmware that meet the following
      criteria:
        * linear framebuffer
        * packed pixel or direct colour mode

This can be automated as well with boot.cfg; I have in mine:

    menu=Boot NetBSD:vesa 1280x800;boot netbsd
    menu=Boot NetBSD (VGA):boot netbsd

Please let me know if I broke anything.

Cheers,
Jared