s390: Add some missing vector patterns.

s390: Add some missing vector patterns.

Some patterns that are detected by the autovectorizer can be supported by
s390.  Add expanders such that autovectorization of these patterns works.

RTL for the builtins used unspec to represent highpart multiplication.
Replace this by the correct RTL to allow further simplification.

gcc/ChangeLog:

	* config/s390/s390.md: Removed unused unspecs.
	* config/s390/vector.md (avg<mode>3_ceil): New expander.
	(uavg<mode>3_ceil): New expander.
	(smul<mode>3_highpart): New expander.
	(umul<mode>3_highpart): New expander.
	* config/s390/vx-builtins.md (vec_umulh<mode>): Remove unspec.
	(vec_smulh<mode>): Remove unspec.

gcc/testsuite/ChangeLog:

	* gcc.target/s390/vector/pattern-avg-1.c: New test.
	* gcc.target/s390/vector/pattern-mulh-1.c: New test.

Signed-off-by: Juergen Christ <jchrist@linux.ibm.com>