[asan] add a flag poison_heap to allow better allocator benchmarking, implemenet malloc_stats() on Linux

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@170685 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/asan/asan_flags.h b/lib/asan/asan_flags.h
index ded2b24..8306170 100644
--- a/lib/asan/asan_flags.h
+++ b/lib/asan/asan_flags.h
@@ -99,6 +99,9 @@
   bool fast_unwind_on_fatal;
   // Use fast (frame-pointer-based) unwinder on malloc/free (if available).
   bool fast_unwind_on_malloc;
+  // Poison (or not) the heap memory on [de]allocation. Zero value is useful
+  // for benchmarking the allocator or instrumentator.
+  bool poison_heap;
 };
 
 Flags *flags();