invoke.texi (Optimize Options): Add anchor for the type-punning blurb.

invoke.texi (Optimize Options): Add anchor for the type-punning blurb.

	* doc/invoke.texi (Optimize Options) <fstrict-aliasing>: Add
	anchor for the type-punning blurb.  Cross-reference "Structures
	unions enumerations and bit-fields implementation".  Provide a
	cast-through-pointer example.  Make final sentence self-contained.
	* doc/implement-c.texi (Structures unions enumerations and
	bit-fields implementation): Cross-reference the type-punning blurb
	in the -fstrict-aliasing documentation.

From-SVN: r137095