fix _mm256_extract_epi64 in msvc2015 and old winsdk

[futz12]

as far as i know, there is no _mm256_extract_epi64 in msvc2015 and old winsdk. so i impl it by hand.

static inline uint64_t _mm256_extract_epi64_fork(__m256i a, const int index)
{
    typedef union {
        __m256i v;
        uint64_t i64[4];
    } extractor;

    extractor u;
    u.v = a;
    
    return u.i64[index];
}

uint64_t copy(uint64_t num) {
    __m256i v;
	v = _mm256_set1_epi64x (num);
	return _mm256_extract_epi64_fork(v, 0);
}

it`s asm in msvc 2015(/O2) is

        vmovq   xmm0, rcx
        vpunpcklqdq xmm0, xmm0, xmm0
        vinsertf128 ymm0, ymm0, xmm0, 1
        vmovq   rax, xmm0
        vzeroupper

in msvc 2017(/O2) is

        vmovq   xmm0, rcx
        vpunpcklqdq xmm0, xmm0, xmm0
        vinsertf128 ymm0, ymm0, xmm0, 1
        vmovq   rax, xmm0
        vzeroupper

vanilla in msvc2017(/O2) is

        vmovq   xmm0, rcx
        vpunpcklqdq xmm0, xmm0, xmm0
        vinsertf128 ymm0, ymm0, xmm0, 1
        vpextrq rax, xmm0, 0
        vzeroupper

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[futz12]

#3548

[jxt1234]

"D:\a\MNN\MNN\source\backend\cpu\x86_x64\avx\GemmInt8.cpp(1549,32): error C2668: '`anonymous-namespace'::_mm256_extract_epi64': ambiguous call to overloaded function"

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