S390: Add target descriptions for vector register sets

S390: Add target descriptions for vector register sets

The IBM z13 has new vector registers v0-v31 which are presented by the
Linux kernel as two additional register sets.  This patch adds XML
descriptions and the respective autogenerated .c and .dat files for
S390 targets with this feature.  Note that supported combinations
include targets with and without a transactional execution facility.

gdb/ChangeLog:

	* features/s390-tevx-linux64.xml: New file.
	* features/s390-vx-linux64.xml: New file.
	* features/s390-vx.xml: New file.
	* features/s390x-tevx-linux64.xml: New file.
	* features/s390x-vx-linux64.xml: New file.
	* features/Makefile (WHICH): Add s390-vx-linux64,
	s390x-vx-linux64, s390-tevx-linux64, and s390x-tevx-linux64.
	(s390-vx-linux64-expedite, s390-tevx-linux64-expedite)
	(s390x-vx-linux64-expedite, s390x-tevx-linux64-expedite): New
	macros.
	* features/s390-tevx-linux64.c: New generated file.
	* features/s390-vx-linux64.c: Likewise.
	* features/s390x-tevx-linux64.c: Likewise.
	* features/s390x-vx-linux64.c: Likewise.
	* regformats/s390-tevx-linux64.dat: Likewise.
	* regformats/s390-vx-linux64.dat: Likewise.
	* regformats/s390x-tevx-linux64.dat: Likewise.
	* regformats/s390x-vx-linux64.dat: Likewise.

gdb/doc/ChangeLog:

	* gdb.texinfo (S/390 and System z Features): Describe new feature
	"org.gnu.gdb.s390.vx".