Merge pull request #1012 from ian-semmle/constexpr

C++: Add Variable.isConstexpr()

cpp/ql/src/semmle/code/cpp/Variable.qll

@@ -121,6 +121,13 @@ class Variable extends Declaration, @variable {
     result.getLValue() = this.getAnAccess()
   }
 
+  /**
+   * Holds if this variable is `constexpr`.
+   */
+  predicate isConstexpr() {
+    this.hasSpecifier("is_constexpr")
+  }
+
   /**
    * Holds if this variable is constructed from `v` as a result
    * of template instantiation. If so, it originates either from a template