Add a full set of CC Mode language variables to js.el.

This will allow js.el to work after maintenance changes in CC Mode, e.g. the
fix to bug #11165.

* lisp/progmodes/js.el (top level): Create a CC Mode derived language called
js-mode and based on Java Mode.
(js-mode): call c-init-language-vars for js-mode.  Remove the direct settings
of several CC Mode language variables which are now defined through the
derived language mechanism.  Call c-set-style and set up the needed style
variables c-block-comment-prefix and c-comment-prefix-regexp.
1 job for master in 61 minutes and 2 seconds (queued for 1 second)
Status Job ID Name Coverage
failed #4131


Name Stage Failure
test-all Test
Makefile:319: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1