Add a way to disable backtracing in malloc debug.

The property libc.debug.malloc.nobacktrace set to non-zero disables
getting backtracing when using mode 1 or mode 10.

Bug: 16874447

(cherry picked from 49de01a5be7bfb07baaea7415647d838383e1b59)

Change-Id: I6bbefe5420b14991fe84c2f849222dcd7cb592bf
diff --git a/libc/bionic/malloc_debug_leak.cpp b/libc/bionic/malloc_debug_leak.cpp
index 7926a1f..837dccc 100644
--- a/libc/bionic/malloc_debug_leak.cpp
+++ b/libc/bionic/malloc_debug_leak.cpp
@@ -47,6 +47,7 @@
 #include <unwind.h>
 
 #include "debug_stacktrace.h"
+#include "malloc_debug_backtrace.h"
 #include "malloc_debug_common.h"
 #include "malloc_debug_disable.h"
 
@@ -311,7 +312,7 @@
         ScopedPthreadMutexLocker locker(&g_hash_table->lock);
 
         uintptr_t backtrace[BACKTRACE_SIZE];
-        size_t numEntries = get_backtrace(backtrace, BACKTRACE_SIZE);
+        size_t numEntries = GET_BACKTRACE(backtrace, BACKTRACE_SIZE);
 
         AllocationEntry* header = reinterpret_cast<AllocationEntry*>(base);
         header->entry = record_backtrace(backtrace, numEntries, bytes);