ART: Clean up includes.

Reduce dependencies to improve incremental build times.
Break up circular dependency involving class_linker-inl.h.

Change-Id: I4be742c5c2b5cd9855beea86630fd68aab76b0db
diff --git a/compiler/utils/arena_bit_vector.cc b/compiler/utils/arena_bit_vector.cc
index ddc0c81..fbbfd84 100644
--- a/compiler/utils/arena_bit_vector.cc
+++ b/compiler/utils/arena_bit_vector.cc
@@ -16,6 +16,7 @@
 
 #include "arena_bit_vector.h"
 
+#include "base/allocator.h"
 #include "base/arena_allocator.h"
 
 namespace art {