fix assembler error. libc_hidden_data_def cannot work on COMMONs,

thus need to initialize stuff with 0 to force it into bss.
All hell can again break loose if future gcc will be smart enough
to ignore it.

libc/stdlib/__uc_malloc.c

@@ -24,8 +24,11 @@ Cambridge, MA 02139, USA.
 #include <unistd.h>
 #include <malloc.h>
 
-void (*__uc_malloc_failed)(size_t size);
-libc_hidden_data_def(__uc_malloc_failed);
+void (*__uc_malloc_failed)(size_t size) = NULL;
+/* Seemingly superfluous assigment of NULL above prevents gas error
+ * ("__uc_malloc_failed can't be equated to common symbol
+ * __GI___uc_malloc_failed") in libc_hidden_data_def: */
+libc_hidden_data_def(__uc_malloc_failed)
 
 void *__uc_malloc(size_t size)
 {
@@ -40,4 +43,4 @@ void *__uc_malloc(size_t size)
 		__uc_malloc_failed(size);
 	}
 }
-libc_hidden_def(__uc_malloc);
+libc_hidden_def(__uc_malloc)