Support for saving and restoring live registers in a slow path.

And use it in suspend check slow paths.

Change-Id: I79caf28f334c145a36180c79a6e2fceae3990c31
diff --git a/compiler/optimizing/locations.cc b/compiler/optimizing/locations.cc
index fce97bd..1c36cdf 100644
--- a/compiler/optimizing/locations.cc
+++ b/compiler/optimizing/locations.cc
@@ -28,7 +28,7 @@
       call_kind_(call_kind),
       stack_mask_(nullptr),
       register_mask_(0),
-      live_registers_(0) {
+      live_registers_() {
   inputs_.SetSize(instruction->InputCount());
   for (size_t i = 0; i < instruction->InputCount(); ++i) {
     inputs_.Put(i, Location());