[Patch Darwin] fix missing __USER_LABEL_PREFIX__ on extended identifiers.

[Iain Sandoe]

I noticed when working on GAS for darwin that we fail to prepend the  
user label prefix for extended identifiers.

fixed as below,
OK for trunk/when?
Iain
gcc:

        * config/darwin.h (ASM_OUTPUT_LABELREF): Add user label prefix
        for extended identifiers.

diff --git a/gcc/config/darwin.h b/gcc/config/darwin.h
index 2425332..3e6efd7 100644
--- a/gcc/config/darwin.h
+++ b/gcc/config/darwin.h
@@ -615,7 +615,7 @@ int darwin_label_is_anonymous_local_objc_name  
(const char *name);
        else if (!strncmp (xname, ".objc_class_name_",  
17))                  \
         fprintf (FILE, "%s",  
xname);                                        \
        else if (xname[0] != '"' && name_needs_quotes  
(xname))               \
-        fprintf (FILE, "\"%s\"",  
xname);                                    \
+        asm_fprintf (FILE, "\"%U%s\"",  
xname);                              \
         
else                                                                 \
          asm_fprintf (FILE, "%U%s",  
xname);                                 \
   } while (0)