message: Temporarily fix compositing by including glew
diff: #include <algorithm>
  #include <cstring>
  +#include <GL/glew.h>
  +
  #include <visionaray/gl/compositing.h>
  #include <visionaray/aligned_vector.h>
  @@ -159,6 +161,8 @@ void cpu_buffer_rt<ColorFormat, DepthFormat>::display_color_buffer() const
  {
  if (DepthFormat != PF_UNSPECIFIED)
  {
  + glPushAttrib( GL_TEXTURE_BIT );
  +
  // Update color texture
  pixel_format_info cinfo = map_pixel_format(ColorFormat);
  @@ -186,6 +190,8 @@ void cpu_buffer_rt<ColorFormat, DepthFormat>::display_color_buffer() const
  // Combine textures using a shader
  impl_->compositor->composite_textures();
  +
  + glPopAttrib();
  }
  else
  {
  