Compile the garbage collector and heap profiler as C++.

Change-Id: I25d8fa821987a3dd6d7109d07fd42dbf2fe0e589
diff --git a/vm/alloc/HeapBitmap.h b/vm/alloc/HeapBitmap.h
index fecc2a9..dd374cc 100644
--- a/vm/alloc/HeapBitmap.h
+++ b/vm/alloc/HeapBitmap.h
@@ -19,6 +19,10 @@
 #include <limits.h>
 #include <stdint.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define HB_OBJECT_ALIGNMENT 8
 #define HB_BITS_PER_WORD (sizeof(unsigned long) * CHAR_BIT)
 
@@ -127,4 +131,8 @@
                             uintptr_t base, uintptr_t max,
                             BitmapSweepCallback *callback, void *callbackArg);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _DALVIK_HEAP_BITMAP */