Fixed the CRT shader for OpenGL frontends (SDL and older Macs)

Shaders/CRT.fsh

@@ -55,7 +55,7 @@ STATIC vec4 scale(sampler2D image, vec2 position, vec2 input_resolution, vec2 ou
     right *= scanline_multiplier;
 
     /* Vertical seperator for shadow masks */
-    bool odd = (int)(position * input_resolution).x & 1;
+    bool odd = bool(int((position * input_resolution).x) & 1);
     if (odd) {
         pos.y += 0.5;
         pos.y = fract(pos.y);