IBM Z: Add vcond_mask expander

IBM Z: Add vcond_mask expander

After adding vec_cmp expanders we have seen various performance
related regression in the testsuite.  These appear to be caused by a
missing vcond_mask definition in the backend.  Fixed with this patch.

The patch fixes the following testsuite fails:

FAIL: gcc.dg/vect/vect-21.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-21.c scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-23.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-23.c scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-24.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-24.c scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-live-6.c -flto -ffat-lto-objects  scan-tree-dump vect "vectorized 1 loops"
FAIL: gcc.dg/vect/vect-live-6.c scan-tree-dump vect "vectorized 1 loops"
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrab\\t%v.?,%v.?,7 6
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesraf\\t%v.?,%v.?,31 6
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrah\\t%v.?,%v.?,15 6
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrlb\\t%v.?,%v.?,7 4
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrlf\\t%v.?,%v.?,31 4
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrlh\\t%v.?,%v.?,15 4
FAIL: gcc.dg/vect/vect-21.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-21.c scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-23.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-23.c scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-24.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-24.c scan-tree-dump-times vect "vectorized 3 loops" 1
FAIL: gcc.dg/vect/vect-live-6.c -flto -ffat-lto-objects  scan-tree-dump vect "vectorized 1 loops"
FAIL: gcc.dg/vect/vect-live-6.c scan-tree-dump vect "vectorized 1 loops"
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrab\\t%v.?,%v.?,7 6
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesraf\\t%v.?,%v.?,31 6
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrah\\t%v.?,%v.?,15 6
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrlb\\t%v.?,%v.?,7 4
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrlf\\t%v.?,%v.?,31 4
FAIL: gcc.target/s390/vector/vcond-shift.c scan-assembler-times vesrlh\\t%v.?,%v.?,15 4

gcc/ChangeLog:

	* config/s390/vector.md ("vcond_mask_<mode><mode>"): New expander.