invoke.texi ([-fprofile-generate], [...]): Fix markup, light copy-editing.

2015-01-03  Sandra Loosemore  <sandra@codesourcery.com>

	gcc/
	* doc/invoke.texi ([-fprofile-generate], [-fprofile-use]):
	Fix markup, light copy-editing.
	([-fauto-profile]): Rewrite to fix formatting and content
	problems.

From-SVN: r219172