rs6000/test: Add vector with length test cases

rs6000/test: Add vector with length test cases

This patch is to add the test coverage for vector with
length feature on rs6000.  Tested on P9 LE, P7 BE and
P9 BE (aix), the results looked fine.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/p9-vec-length-1.h: New test.
	* gcc.target/powerpc/p9-vec-length-2.h: New test.
	* gcc.target/powerpc/p9-vec-length-3.h: New test.
	* gcc.target/powerpc/p9-vec-length-4.h: New test.
	* gcc.target/powerpc/p9-vec-length-5.h: New test.
	* gcc.target/powerpc/p9-vec-length-6.h: New test.
	* gcc.target/powerpc/p9-vec-length-7.h: New test.
	* gcc.target/powerpc/p9-vec-length-8.h: New test.
	* gcc.target/powerpc/p9-vec-length-epil-1.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-2.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-3.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-4.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-5.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-6.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-7.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-8.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-1.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-2.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-3.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-4.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-5.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-6.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-7.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-run-8.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-1.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-2.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-3.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-4.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-5.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-6.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-7.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-8.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-1.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-2.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-3.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-4.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-5.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-6.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-7.c: New test.
	* gcc.target/powerpc/p9-vec-length-full-run-8.c: New test.
	* gcc.target/powerpc/p9-vec-length-run-1.h: New test.
	* gcc.target/powerpc/p9-vec-length-run-2.h: New test.
	* gcc.target/powerpc/p9-vec-length-run-3.h: New test.
	* gcc.target/powerpc/p9-vec-length-run-4.h: New test.
	* gcc.target/powerpc/p9-vec-length-run-5.h: New test.
	* gcc.target/powerpc/p9-vec-length-run-6.h: New test.
	* gcc.target/powerpc/p9-vec-length-run-7.h: New test.
	* gcc.target/powerpc/p9-vec-length-run-8.h: New test.
	* gcc.target/powerpc/p9-vec-length.h: New test.