Separate MemMap from DexFile completely

Create a container class for holding ownership of MemMap and segregate
that functionality to dex_file_loader.  This removes the dependency
between dex_file.cc and mem_map.cc.

Bug: 22322814
Test: make test-art-host
Change-Id: I96db6fd10cdbad774c2f1f85c249418a154fbd52
diff --git a/runtime/class_linker_test.cc b/runtime/class_linker_test.cc
index bd73692..3e92317 100644
--- a/runtime/class_linker_test.cc
+++ b/runtime/class_linker_test.cc
@@ -1466,6 +1466,7 @@
                                                         old_dex_file->Size(),
                                                         location->ToModifiedUtf8(),
                                                         0u,
+                                                        nullptr,
                                                         nullptr));
   {
     WriterMutexLock mu(soa.Self(), *Locks::dex_lock_);