ART: Clean up allocator.h

Move the single-use typedefs to their users. Remove now-unused
includes. Fix up transitive includes.

Test: m
Change-Id: I953d774b28f1e4f3191f96943e3a69ce66aa398a
diff --git a/compiler/utils/swap_space.cc b/compiler/utils/swap_space.cc
index 4f6c915..621a652 100644
--- a/compiler/utils/swap_space.cc
+++ b/compiler/utils/swap_space.cc
@@ -20,6 +20,7 @@
 #include <numeric>
 #include <sys/mman.h>
 
+#include "base/bit_utils.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/mutex.h"