Force inlining on trivial accessors.

Make volatility for GetFieldObject a template parameter.
Move some trivial mirror::String routines to a -inl.h.

Bug: 14285442

Change-Id: Ie23b11d4f18cb15a62c3bbb42837a8aaf6b68f92
diff --git a/runtime/gc/collector/mark_sweep.h b/runtime/gc/collector/mark_sweep.h
index 0c5a0da..bfc70d1 100644
--- a/runtime/gc/collector/mark_sweep.h
+++ b/runtime/gc/collector/mark_sweep.h
@@ -22,7 +22,7 @@
 #include "base/macros.h"
 #include "base/mutex.h"
 #include "garbage_collector.h"
-#include "gc/accounting/space_bitmap.h"
+#include "gc/accounting/heap_bitmap.h"
 #include "immune_region.h"
 #include "object_callbacks.h"
 #include "offsets.h"