Function stbi__psd_test

include/stb/stb_image.h:6081–6086

#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)
{