Added normal mode command `chainloader' as module chain.mod, which
depends on normal.mod and _chain.mod.
* conf/i386-pc.rmk (pkgdata_MODULES): Add `chain.mod'.
(chain_mod_SOURCES, chain_mod_CFLAGS): Variables added.
* include/grub/i386/pc/loader.h (grub_rescue_cmd_chainloader):
Deleted prototype.
* loader/i386/pc/chainloader.c (grub_rescue_cmd_chainloader): All
but arguments parsing moved to ...
(grub_chainloader_cmd): ... here. New function.
* include/grub/i386/pc/chainloader.h: New file.
* loader/i386/pc/chainloader_normal.c: Likewise.
