Rename GlobalSynchronization to Locks

Also address some review comments in common_throws relating to
ToStr<InvokeType> and exception detail messages.

Change-Id: Ibf2c0f147689fa236d349bd7f01eed3c2522552b
diff --git a/src/verifier/reg_type.cc b/src/verifier/reg_type.cc
index 281d96e..f555223 100644
--- a/src/verifier/reg_type.cc
+++ b/src/verifier/reg_type.cc
@@ -385,7 +385,7 @@
 }
 
 std::ostream& operator<<(std::ostream& os, const RegType& rhs)
-    SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_) {
+    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   os << rhs.Dump();
   return os;
 }