Revert "Fully support pairs in the register allocator."

Libcore tests fail.

This reverts commit 41aedbb684ccef76ff8373f39aba606ce4cb3194.

Change-Id: I2572f120d4bbaeb7a4d4cbfd47ab00c9ea39ac6c
diff --git a/compiler/optimizing/locations.cc b/compiler/optimizing/locations.cc
index 990d662..9f2f9ec 100644
--- a/compiler/optimizing/locations.cc
+++ b/compiler/optimizing/locations.cc
@@ -27,7 +27,7 @@
       temps_(instruction->GetBlock()->GetGraph()->GetArena(), 0),
       environment_(instruction->GetBlock()->GetGraph()->GetArena(),
                    instruction->EnvironmentSize()),
-      output_overlaps_(Location::kOutputOverlap),
+      output_overlaps_(true),
       call_kind_(call_kind),
       stack_mask_(nullptr),
       register_mask_(0),