Initialize the out param from backtrace(). (Bug 549561) r=bsmedberg a2.0=tests

tools/trace-malloc/lib/nsTraceMalloc.c

@@ -961,6 +961,7 @@ backtrace(tm_thread *t, int skip, int *immediate_abort)
          * Create a single fake stack frame so that all the tools get
          * data in the correct format.
          */
+        *immediate_abort = 0;
         if (info->size < 1) {
             PR_ASSERT(!info->buffer); /* !info->size == !info->buffer */
             info->buffer = __libc_malloc(1 * sizeof(void*));