ART: Introduce thread-current-inl.h

Factor out Thread::Current() code into its own -inl file to remove
transitive includes.

This requires at the same time correcting mutex.h, i.e., moving
some functions into mutex-inl.h.

Test: m test-art-host
Change-Id: I88f888b604e0897368d9b483edce6ce4332dd9c9
diff --git a/compiler/optimizing/intrinsics_arm_vixl.cc b/compiler/optimizing/intrinsics_arm_vixl.cc
index 1a33b0e..19a3eb9 100644
--- a/compiler/optimizing/intrinsics_arm_vixl.cc
+++ b/compiler/optimizing/intrinsics_arm_vixl.cc
@@ -26,7 +26,7 @@
 #include "mirror/reference.h"
 #include "mirror/string.h"
 #include "scoped_thread_state_change-inl.h"
-#include "thread-inl.h"
+#include "thread-current-inl.h"
 
 #include "aarch32/constants-aarch32.h"