S/390: Set default function alignment to 16.

S/390: Set default function alignment to 16.

gcc/ChangeLog:

2018-07-17  Robin Dapp  <rdapp@linux.ibm.com>

	* config/s390/s390.c (s390_default_align): Set default function
	alignment to 16.
	(s390_override_options_after_change): Call s390_default align.
	(s390_option_override_internal): Call s390_default_align.
	(TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE): Define.

gcc/testsuite/ChangeLog:

2018-07-17  Robin Dapp  <rdapp@linux.ibm.com>

	* gcc.target/s390/function-align1.c: New test.
	* gcc.target/s390/function-align2.c: New test.
	* gcc.target/s390/function-align3.c: New test.

From-SVN: r262817