Fix "making delay-mode-hooks buffer-local" message

On evaluation I am always getting 
```
Making delay-mode-hooks buffer-local while locally let-bound!
```

Fix this by avoiding let; `delay-mode-hooks` need not be let-bound because it's a permanent local variable.

Not an issue, I have added that. But why so? They are not executed anyways, besides that there are other hooks: `major-mode-hook` and `after-change-major-mode-hook`.  


I actually have a more general concern around this code. It is used for java and clojure only. Given that all what is needed is a font lock, why not have optimized dedicated functions that do exactly that. 

For clojure there is already a dedicated function `cider-font-lock-as-clojure` which can simply call `clojure-mode-font-lock-setup`.