ART: Factor out gAborting

Cut dependencies on base/logging.h by moving gAborting to its
own header. Leave the static storage in logging.cc.

Test: m
Change-Id: Ib2ca880e15f9cb50cb9aab803784826bb46efb5e
diff --git a/runtime/base/mutex.h b/runtime/base/mutex.h
index 9a037b5..7077298 100644
--- a/runtime/base/mutex.h
+++ b/runtime/base/mutex.h
@@ -27,7 +27,7 @@
 #include <android-base/logging.h>
 
 #include "atomic.h"
-#include "base/logging.h"  // For gAborting.
+#include "base/aborting.h"
 #include "base/macros.h"
 #include "globals.h"