Fixed unused-but-set-variable warning.

3rdparty/stb_image/stb_image.c

@@ -2951,7 +2951,7 @@ static int shiftsigned(int v, int shift, int bits)
 static stbi_uc *bmp_load(stbi *s, int *x, int *y, int *comp, int req_comp)
 {
    uint8 *out;
-   unsigned int mr=0,mg=0,mb=0,ma=0, fake_a=0;
+   unsigned int mr=0,mg=0,mb=0,ma=0;
    stbi_uc pal[256][4];
    int psize=0,i,j,compress=0,width;
    int bpp, flip_vertically, pad, target, offset, hsz;