Fix variable-shadowing warnings that appear in VS2015 on /W4

stb_image.h

@@ -3502,7 +3502,7 @@ static int stbi__zbuild_huffman(stbi__zhuffman *z, stbi_uc *sizelist, int num)
          z->size [c] = (stbi_uc     ) s;
          z->value[c] = (stbi__uint16) i;
          if (s <= STBI__ZFAST_BITS) {
-            int k = stbi__bit_reverse(next_code[s],s);
+            k = stbi__bit_reverse(next_code[s],s);
             while (k < (1 << STBI__ZFAST_BITS)) {
                z->fast[k] = fastv;
                k += (1 << s);
@@ -4111,8 +4111,7 @@ static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 r
          }
          if (img_n != out_n) {
             // insert alpha = 255
-            stbi_uc *cur = a->out + stride*j;
+            cur = a->out + stride*j;
-            int i;
             if (img_n == 1) {
                for (i=x-1; i >= 0; --i) {
                   cur[i*2+1] = 255;
@@ -4909,8 +4908,8 @@ static stbi_uc *stbi__tga_load(stbi__context *s, int *x, int *y, int *comp, int
 
    if ( !tga_indexed && !tga_is_RLE) {
       for (i=0; i < tga_height; ++i) {
-         int y = tga_inverted ? tga_height -i - 1 : i;
+         int row = tga_inverted ? tga_height -i - 1 : i;
-         stbi_uc *tga_row = tga_data + y*tga_width*tga_comp;
+         stbi_uc *tga_row = tga_data + row*tga_width*tga_comp;
          stbi__getn(s, tga_row, tga_width * tga_comp);
       }
    } else  {
@@ -5351,7 +5350,6 @@ static stbi_uc *stbi__pic_load_core(stbi__context *s,int width,int height,int *c
 
                   if (count >= 128) { // Repeated
                      stbi_uc value[4];
-                     int i;
 
                      if (count==128)
                         count = stbi__get16be(s);
@@ -5593,7 +5591,7 @@ static stbi_uc *stbi__process_gif_raster(stbi__context *s, stbi__gif *g)
          bits |= (stbi__int32) stbi__get8(s) << valid_bits;
          valid_bits += 8;
       } else {
-         stbi__int32 code = bits & codemask;
+         code = bits & codemask;
          bits >>= codesize;
          valid_bits -= codesize;
          // @OPTIMIZE: is there some way we can accelerate the non-clear path?