* configure.in: Change linux to default to elf. Using
i[345]86-*-linuxaout will build a linker which defaults to a.out.
* config/i386-laout.mt: Rename from old config/i386-linux.mt.
* config/i386-linux.mt: Rename from old config/i386-lelf.mt.
* config/i386-lelf.mt: Remove.