TextureConverter: Use integer math for swizzling

also move int(efb_coord) -> float(ogl_fb_coord) into WriteSampleColor

Source/Core/VideoBackends/OGL/Src/ProgramShaderCache.cpp

@@ -584,6 +584,9 @@ void ProgramShaderCache::CreateHeader ( void )
 		"#define float2 vec2\n"
 		"#define float3 vec3\n"
 		"#define float4 vec4\n"
+		"#define int2 ivec2\n"
+		"#define int3 ivec3\n"
+		"#define int4 ivec4\n"
 
 		// hlsl to glsl function translation
 		"#define frac fract\n"