* config/i386/x86-64linux.mh: New file.

* config/i386/x86-64linux.mh: New file.
* config/i386/x86-64linux.mt: New file.
* config/i386/nm-x86_64.h: New file.
* x86-64-linux-tdep.c: New file.
* x86-64-linux-nat.c: New file.
* x86-64-tdep.c: New file.
* x86-64-tdep.h: New file.
* i386-tdep.h: New file.
* i387-nat.c: Include i386-tdep.h when multiarch.
* i387-tdep.c: Ditto.
* config/djgpp/fnchange.lst: Add entries for x86_64-linux-tdep.c
and x86_64-linux-nat.c
* Makefile.in: Add x86_64-linux-tdep.o, x86_64-tdep.o,
x86_64-linux-tdep.o, x86_64-nat.o, update dependencies.