2018-03-05  Sandra Loosemore  <sandra@codesourcery.com>

	gcc/
	* doc/configfiles.texi (Configuration Files): Move info about
	conditionalizing $target-protos.h to...
	* doc/sourcebuild.texi (Back End): Here.  Explain how $target.h
	differs from $target-protos.h.

From-SVN: r258240