rs6000.c (rs6000_override_options): Increase maximum skip to 15.

	* config/rs6000/rs6000.c (rs6000_override_options): Increase
	maximum skip to 15.  Set function alignment, jump alignment, and
	loop alignment to 16 for processors that form dispatch groups.
	(rs6000_rtx_costs): Outer code is used.

From-SVN: r86670