Prepare for removal of tinyxml from homebrew-core

[scpeters]

As tinyxml has been removed from urdfdom in ros/urdfdom#185, there is a good chance that tinyxml will be removed from homebrew-core soon (see Homebrew/homebrew-core#119829). As tinyxml is still used by sdformat9 and gazebo11, we should prepare to fork the tinyxml formula into this tap to support these formulae.

• Use brew extract to create a tinyxml1 formula in osrf/simulation that conflicts with tinyxml and build a bottle for it
  • tinyxml1 extracted from homebrew/core/tinyxml #2522
• Rebuild bottles depending on urdfdom 4.0.0
  • Rebuild bottles after urdfdom 4.0.0 is merged #2505
  • Rebuild gz-sensors, gz-sim, gz-launch, gz-collection
    • Citadel sdformat9, gazebo11: use tinyxml1 #2526
    • Fortress Rebuild fortress bottles for urdfdom 4.0.0 #2524
    • Garden Rebuild garden bottles for urdfdom 4.0.0 #2523
    • Harmonic Rebuild more harmonic bottles for urdfdom 4.0.0 #2525
• sdformat9 to depend on tinyxml1 sdformat9, gazebo11: use tinyxml1 #2526
• gazebo11 to depend on tinyxml1 sdformat9, gazebo11: use tinyxml1 #2526

[scpeters]

It looks like the list of dependencies is cached within each bottle, so any bottle that even indirectly depended on tinyxml via urdfdom (such as gz-sensors*, gz-sim*, gz-launch*, and gz-collections) will need to be rebuilt in order to register the change to depending on tinyxml2.