wined3d: Make sure the color buffer is not modified by depth_blt().

dlls/wined3d/drawprim.c

@@ -760,15 +760,16 @@ static void depth_blt(IWineD3DDevice *iface, GLuint texture) {
     IWineD3DDeviceImpl *This = (IWineD3DDeviceImpl *)iface;
     GLint old_binding = 0;
 
-    glPushAttrib(GL_ENABLE_BIT | GL_DEPTH_BUFFER_BIT);
+    glPushAttrib(GL_ENABLE_BIT | GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
 
     glDisable(GL_CULL_FACE);
-    glDisable(GL_BLEND);
+    glEnable(GL_BLEND);
     glDisable(GL_ALPHA_TEST);
     glDisable(GL_SCISSOR_TEST);
     glDisable(GL_STENCIL_TEST);
     glEnable(GL_DEPTH_TEST);
     glDepthFunc(GL_ALWAYS);
+    glBlendFunc(GL_ZERO, GL_ONE);
 
     GL_EXTCALL(glActiveTextureARB(GL_TEXTURE0_ARB));
     glGetIntegerv(GL_TEXTURE_BINDING_2D, &old_binding);