add EvaluateAsInt compat function for latest clang

the old EvaluateAsInt method has been dropped as from current clang

Change-Id: Ie30d1547ad8de777badff4b380d2fc9fb261e8fe
Reviewed-on: https://gerrit.libreoffice.org/64107
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/staticconstfield.cxx

@@ -130,7 +130,7 @@ bool StaticConstField::TraverseConstructorInitializer(CXXCtorInitializer* init)
     else
     {
         APSInt x1;
-        if (initexpr->EvaluateAsInt(x1, compiler.getASTContext()))
+        if (compat::EvaluateAsInt(initexpr, x1, compiler.getASTContext()))
         {
             value = x1.toString(10);
             found = true;