re PR target/83250 (_mm256_zextsi128_si256 missing for AVX2 zero extension)

re PR target/83250 (_mm256_zextsi128_si256 missing for AVX2 zero extension)

	PR target/83250
	PR target/91340
	* config/i386/avxintrin.h (_mm256_zextpd128_pd256,
	_mm256_zextps128_ps256, _mm256_zextsi128_si256): New intrinsics.
	* config/i386/avx512fintrin.h (_mm512_zextpd128_pd512,
	_mm512_zextps128_ps512, _mm512_zextsi128_si512, _mm512_zextpd256_pd512,
	_mm512_zextps256_ps512, _mm512_zextsi256_si512): Likewise.

	* gcc.target/i386/avx-typecast-1.c: New test.
	* gcc.target/i386/avx-typecast-2.c: New test.
	* gcc.target/i386/avx512f-typecast-2.c: New test.

From-SVN: r274313