re PR middle-end/83665 (Big code size regression and some code quality improvement...

re PR middle-end/83665 (Big code size regression and some code quality improvement at Jan 2 2018)

	PR middle-end/83665
	* params.def (inline-min-speedup): Increase from 8 to 15.
	(max-inline-insns-auto): Decrease from 40 to 30.
	* ipa-split.c (consider_split): Add some buffer for function to
	be considered inlining candidate.
	* invoke.texi (max-inline-insns-auto, inline-min-speedup): UPdate
	default values.

From-SVN: r257582