Add constexpr annotations to LSEVisitor member functions.

Newer versions of clang rightly warn about LSEVisitor::Value::Equals
not being a constexpr function because it calls the non-constexpr
function LSEVisitor::IsValid(). Silence the warning by marking that
function and its callees as constexpr.

Change-Id: Ib3c36bd02232f8e465eac4eceabfa7ac069a634f
1 file changed