The second phase of syscons reorganization.

The second phase of syscons reorganization.

- Split syscons source code into manageable chunks and reorganize
  some of complicated functions.

- Many static variables are moved to the softc structure.

- Added a new key function, PREV.  When this key is pressed, the vty
  immediately before the current vty will become foreground.  Analogue
  to PREV, which is usually assigned to the PrntScrn key.
  PR: kern/10113
  Submitted by: Christian Weisgerber <naddy@mips.rhein-neckar.de>

- Modified the kernel console input function sccngetc() so that it
  handles function keys properly.

- Reorganized the screen update routine.

- VT switching code is reorganized.  It now should be slightly more
  robust than before.

- Added the DEVICE_RESUME function so that syscons no longer hooks the
  APM resume event directly.

- New kernel configuration options: SC_NO_CUTPASTE, SC_NO_FONT_LOADING,
  SC_NO_HISTORY and SC_NO_SYSMOUSE.
  Various parts of syscons can be omitted so that the kernel size is
  reduced.

  SC_PIXEL_MODE
  Made the VESA 800x600 mode an option, rather than a standard part of
  syscons.

  SC_DISABLE_DDBKEY
  Disables the `debug' key combination.

  SC_ALT_MOUSE_IMAGE
  Inverse the character cell at the mouse cursor position in the text
  console, rather than drawing an arrow on the screen.
  Submitted by: Nick Hibma (n_hibma@FreeBSD.ORG)

  SC_DFLT_FONT
  makeoptions "SC_DFLT_FONT=_font_name_"
  Include the named font as the default font of syscons.  16-line,
  14-line and 8-line font data will be compiled in.  This option replaces
  the existing STD8X16FONT option, which loads 16-line font data only.

- The VGA driver is split into /sys/dev/fb/vga.c and /sys/isa/vga_isa.c.

- The video driver provides a set of ioctl commands to manipulate the
  frame buffer.

- New kernel configuration option: VGA_WIDTH90
  Enables 90 column modes: 90x25, 90x30, 90x43, 90x50, 90x60.  These
  modes are mot always supported by the video card.
  PR: i386/7510
  Submitted by: kbyanc@freedomnet.com and alexv@sui.gda.itesm.mx.

- The header file machine/console.h is reorganized; its contents is now
  split into sys/fbio.h, sys/kbio.h (a new file) and sys/consio.h
  (another new file).  machine/console.h is still maintained for
  compatibility reasons.

- Kernel console selection/installation routines are fixed and
  slightly rebumped so that it should now be possible to switch between
  the interanl kernel console (sc or vt) and a remote kernel console
  (sio) again, as it was in 2.x, 3.0 and 3.1.

- Screen savers and splash screen decoders
  Because of the header file reorganization described above, screen
  savers and splash screen decoders are slightly modified.  After this
  update, /sys/modules/syscons/saver.h is no longer necessary and is
  removed.