make reserved word checking case sensitive

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/SwiftCodegen.java

@@ -204,6 +204,11 @@ public class SwiftCodegen extends DefaultCodegen implements CodegenConfig {
 
     }
 
+    @Override
+    protected boolean isReservedWord(String word) {
+        return word != null && reservedWords.contains(word); //don't lowercase as super does
+    }
+
     @Override
     public String escapeReservedWord(String name) {
         return "_" + name;  // add an underscore to the name