glxheads: exercise multiple GLX connections (any key = exit)
Usage:
  glxheads xdisplayname ...
Example:
  glxheads :0 mars:0 venus:1
Name: :0.0
  Display:     0xda2340
  Window:      0x1800002
  Context:     0xfbd1c0
  GL_VERSION:  4.2.11762 Compatibility Profile Context
  GL_VENDOR:   ATI Technologies Inc.
  GL_RENDERER: AMD Radeon HD 7800 Series