message: fix bloom upsample shaders
  We were not using the correct offsets, however because everything
  was so blurry, it wasn't obvious that something was wrong.
  This should result in a bit smoother bloom effect.
diff: @@ -36,8 +36,8 @@ fragment {
  highp vec2 uv = variable_vertex.xy;
  #if defined(TARGET_MOBILE)
  - highp float du = materialParams.resolution.z;
  - highp float dv = materialParams.resolution.w;
  + highp float du = 0.5 * materialParams.resolution.z;
  + highp float dv = 0.5 * materialParams.resolution.w;
  vec3 c;
  c = textureLod(materialParams_source, uv + vec2(-du, -dv), lod).rgb;
  c += textureLod(materialParams_source, uv + vec2( du, -dv), lod).rgb;
  @@ -45,8 +45,8 @@ fragment {
  c += textureLod(materialParams_source, uv + vec2(-du, dv), lod).rgb;
  postProcess.color.rgb = c * 0.25;
  #else
  - highp float du = 2.0 * materialParams.resolution.z;
  - highp float dv = 2.0 * materialParams.resolution.w;
  + highp float du = materialParams.resolution.z;
  + highp float dv = materialParams.resolution.w;
  vec3 c0, c1;
  c0 = textureLod(materialParams_source, uv + vec2(-du, -dv), lod).rgb;
  c0 += textureLod(materialParams_source, uv + vec2( du, -dv), lod).rgb;
  