sparc: Convert to mem_thread_fence.

sparc: Convert to mem_thread_fence.

        * config/sparc/predicates.md (zero_or_v7_operand): New.
        * config/sparc/sparc.c (sparc_emit_membar_for_model): New.
        * config/sparc/sparc-protos.h: Update.
        * config/sparc/sync.md (mem_thread_fence): New.
        (memory_barrier): Use sparc_emit_membar_for_model.
        (membar, *membar_empty, *membar_storestore, *membar_storeload): New.
        (*membar_v8): Accept and ignore the membar mask.
        (*membar): Accept and print the membar mask.

From-SVN: r181848