S390: Add new hwcap values for new cpu architecture - arch12.

The new hwcap values indicate support for:
- Vector packed decimal facility
- Vector enhancements facility 1
- Guarded storage facility

Note: arch12 is NOT the official name of the new CPU.
It refers to the edition number of the Principle of Operations manual.

ChangeLog:

	* sysdeps/s390/dl-procinfo.c (_dl_s390_cap_flags):
	Add vxd, vxe, gs flag.
	* sysdeps/s390/dl-procinfo.h: Add HWCAP_S390_VXD, HWCAP_S390_VXE,
	HWCAP_S390_GS capability.
	* sysdeps/unix/sysv/linux/s390/bits/hwcap.h
	(HWCAP_S390_VXD, HWCAP_S390_VXE, HWCAP_S390_GS): Define.