Function stbi__psd_test

lite/example/cpp_example/mge/cv/stb_image.h:6694–6698

#ifndef STBI_NO_PSD
static int stbi__psd_test(stbi__context* s) {
    int r = (stbi__get32be(s) == 0x38425053);
    stbi__rewind(s);
    return r;
}

static int stbi__psd_decode_rle(stbi__context* s, stbi_uc* p, int pixelCount) {
    int count, nleft, len;