ART: Clean up heap headers

Use more forward declarations for accounting structures and spaces.
Factor out structs to reduce header surface. Remove heap include where
unnecessary. Fix up transitive users. Move some debug-only code out
of line.

Test: m test-art-host
Change-Id: I16db4aaa803f39e155ce6e1b0778b7e393dcbb17
diff --git a/runtime/mem_map_test.cc b/runtime/mem_map_test.cc
index aa306ac..5f027b1 100644
--- a/runtime/mem_map_test.cc
+++ b/runtime/mem_map_test.cc
@@ -16,6 +16,8 @@
 
 #include "mem_map.h"
 
+#include <sys/mman.h>
+
 #include <memory>
 
 #include "common_runtime_test.h"