Optimize vpermtiw/b to vpunpcklqdq for certain cases.

Optimize vpermtiw/b to vpunpcklqdq for certain cases.

Assembly Optimization like:
-       vmovq   %xmm0, %xmm2
-       vmovdqa .LC0(%rip), %xmm0
        vmovq   %xmm1, %xmm1
-       vpermi2w        %xmm1, %xmm2, %xmm0
+       vmovq   %xmm0, %xmm0
+       vpunpcklqdq     %xmm1, %xmm0, %xmm0

...

-.LC0:
-       .value  0
-       .value  1
-       .value  2
-       .value  3
-       .value  8
-       .value  9
-       .value  10
-       .value  11

gcc/ChangeLog:

	PR target/105033
	* config/i386/sse.md (*vec_concatv4si): Extend to ..
	(*vec_concat<mode>): .. V16QI and V8HImode.
	(*vec_concatv16qi_permt2): New pre_reload define_insn_and_split.
	(*vec_concatv8hi_permt2): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr105033.c: New test.