S390: Increase function alignment to 16 bytes.

Set the default function alignment to 16 bytes in order to
get rid of some unwanted performance effects.

Please see also GCC commit "S/390: Set default function
alignment to 16." (Subversion revision 262817)

ChangeLog:

	* sysdeps/s390/s390-64/sysdep.h(ENTRY): Use alignment of 16byte.
	* sysdeps/s390/s390-32/sysdep.h: Likewise.