* conf/i386-pc.rmk (GRUB_MEMORY_MACHINE_LINK_ADDR): New variable.
(kernel_img_LDFLAGS): Use `GRUB_MEMORY_MACHINE_LINK_ADDR' as link
address.
(grub_mkimage_CFLAGS): Propagate `GRUB_MEMORY_MACHINE_LINK_ADDR' as
a C macro.
* include/grub/i386/pc/memory.h (GRUB_MEMORY_MACHINE_UPPER): New macro.
Indicates start of upper memory.
* util/i386/pc/grub-mkimage.c: Include `<grub/machine/memory.h>'.
(generate_image): Abort when image size is big enough to corrupt
upper memory.
* include/grub/i386/pc/vga.h: Include `<grub/machine/memory.h>'.
(GRUB_MEMORY_MACHINE_VGA_ADDR): Alias for `GRUB_MEMORY_MACHINE_UPPER'.
* term/i386/pc/vga.c (VGA_MEM): Use `GRUB_MEMORY_MACHINE_VGA_ADDR'
instead of hardcoding 0xA0000.
* video/i386/pc/vbe.c: Include `<grub/machine/vga.h>'.
(grub_vbe_set_video_mode): Use `GRUB_MEMORY_MACHINE_VGA_ADDR'
instead of hardcoding 0xA0000.