Ignore keywords during transformations
After this patch rust keywords will not have case transformations applied
// before patch
upper!(fn test(){}); // render `FN TEST() {}`
// after patch
upper!(fn test(){}); // render `fn TEST() {}`
After this patch rust keywords will not have case transformations applied
// before patch
upper!(fn test(){}); // render `FN TEST() {}`
// after patch
upper!(fn test(){}); // render `fn TEST() {}`