Fix msvc compiler warnings

With all warnings enabled, cl emits a 'C4127: conditional expression is constant'.
Just remove the offending line since uit's dead code and the comment for
it is clear emough.
Also fix a 'C4334' warning implicit 64bit conversion of 32bit shift result.

lodepng.cpp

@@ -2624,12 +2624,10 @@ static int lodepng_color_mode_equal(const LodePNGColorMode* a, const LodePNGColo
   /*if one of the palette sizes is 0, then we consider it to be the same as the
   other: it means that e.g. the palette was not given by the user and should be
   considered the same as the palette inside the PNG.*/
-  if(1/*a->palettesize != 0 && b->palettesize != 0*/) {
-    if(a->palettesize != b->palettesize) return 0;
-    for(i = 0; i != a->palettesize * 4; ++i)
-    {
-      if(a->palette[i] != b->palette[i]) return 0;
-    }
+  if(a->palettesize != b->palettesize) return 0;
+  for(i = 0; i != a->palettesize * 4; ++i)
+  {
+    if(a->palette[i] != b->palette[i]) return 0;
   }
   return 1;
 }
@@ -3476,7 +3474,7 @@ unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
   {
     size_t palettesize = mode_out->palettesize;
     const unsigned char* palette = mode_out->palette;
-    size_t palsize = 1u << mode_out->bitdepth;
+    size_t palsize = size_t( 1u ) << mode_out->bitdepth;
     /*if the user specified output palette but did not give the values, assume
     they want the values of the input color type (assuming that one is palette).
     Note that we never create a new palette ourselves.*/