mmix.h (ASM_OUTPUT_EXTERNAL): Define to default_elf_asm_output_external.
Whoops. When un-disabling visibility support for mmix, I missed that
some of the newly enabled tests were FAILs, for not emitting .hidden
for references to external declarations. This takes care of
gcc.dg/visibility-14.c .. -19.c, and gcc.dg/visibility-23.c.
gcc:
* config/mmix/mmix.h (ASM_OUTPUT_EXTERNAL): Define to
default_elf_asm_output_external.