* lisp/progmodes/antlr-mode.el: Fix bootstrap failure

* lisp/progmodes/antlr-mode.el: Fix bootstrap failure

(antlr-mode): Remove compatibility code with older CC-mode.
This somehow appears to fix the error:

    In antlr-mode:
    progmodes/antlr-mode.el:2426:20: Error: `c-init-language-vars' defined
        after use in (c-init-language-vars) (missing `require' of a library
        file?)
    progmodes/antlr-mode.el:2427:26: Warning: c-init-language-vars called
        with 0 arguments, but requires 1

No idea what caused the error to appear after the previous patch either.