allow the use of old console code and update elf_object not to rely on EM_ALPHA value.

allow the use of old console code and update elf_object not to rely on EM_ALPHA value.

base/loader/elf_object.cc:
    EM_ALPHA value isn't official, so perhaps we shouldn't use it
dev/alpha_console.cc:
dev/alpha_console.hh:
    this change allows the use of old console code

--HG--
extra : convert_revision : cfacd64ae7fd2595158ca1a83ebcdb66ee7e119b