Fix WebGL gamma correction;

Ugh, WebGL doesn't have sRGB backbuffers.

src/modules/graphics/graphics.c

@@ -358,7 +358,9 @@ Color lovrGraphicsGetBackgroundColor() {
 
 void lovrGraphicsSetBackgroundColor(Color color) {
   state.backgroundColor = state.linearBackgroundColor = color;
+#ifndef LOVR_WEBGL
   gammaCorrect(&state.linearBackgroundColor);
+#endif
 }
 
 void lovrGraphicsGetBlendMode(BlendMode* mode, BlendAlphaMode* alphaMode) {
@@ -766,7 +768,9 @@ void lovrGraphicsFlushMesh(Mesh* mesh) {
 }
 
 void lovrGraphicsClear(Color* color, float* depth, int* stencil) {
+#ifndef LOVR_WEBGL
   if (color) gammaCorrect(color);
+#endif
   if (color || depth || stencil) lovrGraphicsFlush();
   lovrGpuClear(state.canvas ? state.canvas : state.camera.canvas, color, depth, stencil);
 }

src/resources/shaders.c

@@ -94,6 +94,9 @@ const char* lovrShaderFragmentSuffix = ""
 "  colors(lovrColor, lovrDiffuseTexture, texCoord); \n"
 "#else \n"
 "  lovrCanvas[0] = color(lovrColor, lovrDiffuseTexture, texCoord); \n"
+#ifdef LOVR_WEBGL
+"  lovrCanvas[0].rgb = pow(lovrCanvas[0].rgb, vec3(.4545)); \n"
+#endif
 "#endif \n"
 "}";