DRAFT x86_64: build: Cater for M2-Planet.
XXX scaffold tests run,
* MES_DEBUG=3 bin/mes-m2 segfaults in gc_init.
* kaem.run: Define __<cpu>__.
* kaem.x86_64,
lib/linux/x86_64-mes-m2/_exit.c,
lib/linux/x86_64-mes-m2/_write.c,
lib/linux/x86_64-mes-m2/crt1.M1,
lib/linux/x86_64-mes-m2/crt1.c,
lib/linux/x86_64-mes-m2/syscall.c,
lib/m2/x86_64/ELF-x86_64.hex2,
lib/m2/x86_64/x86_64_defs.M1: New files.
* build-aux/build.sh.in: Also allow kaem build for X86_64.
* include/mes/lib-mini.h[__M2__ && __x86_64__](M2_PTR_SIZE): Define as
8.
* include/mes/mes.h[__M2__ && __x86_64__](M2_CELL_SIZE): Define as 24.
* lib/x86_64-mes/x86_64.M1 (add____$i8,%rbp, mov____%rdi,%rbp): New
defines.
c4e58b5a18