S/390: Implement vcond expander for V1TI,V1TF

S/390: Implement vcond expander for V1TI,V1TF

Currently gcc does not emit wf{c,k}* instructions when comparing long
double values.  Middle-end actually adds them in the first place, but
then veclower pass replaces them with floating point register pair
operations, because the corresponding expander is missing.

gcc/ChangeLog:

2019-10-01  Ilya Leoshkevich  <iii@linux.ibm.com>

	PR target/77918
	* config/s390/vector.md (V_HW): Add V1TI in order to make
	vcond$a$b generate vcondv1tiv1tf.

From-SVN: r276408