[syslinux] Patch to add option-key menus (similar to SuSE patch)

[Gordon Schumacher]

I've written a patch to add option-key submenus to menu.c32 and
vesamenu.c32 for doing things like changing the video mode.  This was
inspired the the patch that SuSE applies to the syslinux family and
Grub, without the ugly pseudo-PostScript spaghetti.

The patch may be found at
http://www.valleyhold.org/~gordons/syslinux-optmenus.diff (it's over
30K, so posting it here didn't seem appropriate).

Let me know what you think - I hope this can make it as mainline code!
 It's almost certainly not fully debugged yet - I'm sure you can break
it if you try - but it should be a good (functional) start.

Here's a short bit of documentation:

OPTMENU F1...F12 TITLE submenutitle
Begins a new submenu, triggered by the appropriate function key.  Do
not assign a function key that you have already assigned to the "F1
textfile background" function to display full-screen help, or this
menu will never be displayed.

OPTMENU F1...F12 ENTRY displaytext
Begins a new entry in the indicated submenu.  The text given is what
will be displayed for that menu option.

OPTMENU F1...F12 VALUE kernelappend
Sets the string that will be added to the APPEND string of the
currently selected boot entry.  This is applied to the last ENTRY.

OPTMENU F1...F12 DEFAULT entrynum
Selects which entry in the indicated submenu will be selected by default.


OPTMENUS F1 F2 F3...
To be used in a LABEL section, this selects which fkey submenus will
be active for the current LABEL.


Example config file:

TIMEOUT 200
DEFAULT /boot/vesamenu.c32
MENU TITLE test menu

OPTMENU F2 TITLE Video mode
  OPTMENU F2 ENTRY Text (80 x 25)
  OPTMENU F2 VALUE vga=normal
  OPTMENU F2 ENTRY Text (80 x 50)
  OPTMENU F2 VALUE vga=ext
  OPTMENU F2 ENTRY 640 x 480
  OPTMENU F2 VALUE vga=785
  OPTMENU F2 ENTRY 800 x 600
  OPTMENU F2 VALUE vga=788
  OPTMENU F2 ENTRY 1024 x 768
  OPTMENU F2 VALUE vga=791
  OPTMENU F2 ENTRY 1280 x 1024
  OPTMENU F2 VALUE vga=794
  OPTMENU F2 ENTRY 1600 x 1200
  OPTMENU F2 VALUE vga=798
  OPTMENU F2 DEFAULT 4
OPTMENU F3 TITLE Virtualization
  OPTMENU F3 ENTRY Run in VMware
  OPTMENU F3 VALUE load=vmware*
  OPTMENU F3 ENTRY Run Native


LABEL standard
  MENU LABEL Normal kernel
  KERNEL /boot/vmlinuz
  APPEND initrd=/boot/initrd.gz splash=silent ramdisk_size=6379
root=/dev/ram0 rw changes=slaxchanges
  OPTMENUS F2 F3

LABEL kdebug
  MENU LABEL Debugging Kernel
  KERNEL /boot/vmlinuz_devel
  APPEND initrd=/boot/initrd_devel.gz splash=silent ramdisk_size=13239
root=/dev/ram0 rw changes=slaxchanges
  OPTMENUS F2

LABEL memtest86
  MENU LABEL Memtest86+ Memory Tester
  KERNEL /boot/mt86p