Add clarifying comment

Change-Id: Ie891404a4d21e1917e5e653737e35257df3dfcae

compilerplugins/clang/simplifybool.cxx

@@ -32,6 +32,15 @@ enum class Value { Unknown, False, True };
 
 Value getValue(Expr const * expr) {
     if (expr->getType()->isBooleanType()) {
+        // Instead going via Expr::isCXX11ConstantExpr would turn up excatly one
+        // additional place in svx/source/dialog/framelinkarray.cxx
+        //
+        //   const bool DIAG_DBL_CLIP_DEFAULT = false;
+        //   ...
+        //   ... = mxImpl.get() ? mxImpl->mbDiagDblClip : DIAG_DBL_CLIP_DEFAULT;
+        //
+        // where it is unclear whether it is not actually better to consider
+        // DIAG_DBL_CLIP_DEFAULT a tunable parameter (and thus not to simplify):
         auto lit
             = dyn_cast<CXXBoolLiteralExpr>(ignoreParenImpCastAndComma(expr));
         if (lit != nullptr) {