Avoid aliases when compiling with Apple's CC for PCBIOS machine
* kern/misc.c [APPLE_CC] (memcpy): new function
[APPLE_CC] (memmove): likewise
[APPLE_CC && !GRUB_UTIL] (grub_err_printf): likewise
(memcpy): define alias conditionaly on !APPLE_CC
(memset): likewise
(abort): likewise
* include/grub/misc.h (memove): don't define when both GRUB_UTIL and
APPLE_CC are defined
* include/grub/list.h [APPLE_CC] (grub_assert_fail): new function
(grub_assert_fail): make prototype conditional