lang.opt: Refer to the GCC internals documentation instead of c.opt.

lang.opt: Refer to the GCC internals documentation instead of c.opt.

fortran/
	* lang.opt: Refer to the GCC internals documentation instead of c.opt.

ada/
	* lang.opt: Refer to the GCC internals documentation instead of c.opt.

java/
	* lang.opt: Refer to the GCC internals documentation instead of c.opt.

treelang/
	* lang.opt: Refer to the GCC internals documentation instead of c.opt.

From-SVN: r98012