remove mach.rb from homebrew-fork
rm homebrew-fork module ObserverPathnameExtension
remove numerous unused methods from homebrew-fork

Covering files:
* extend/fileutils.rb
* hardware.rb
* utils.rb
pare back homebrew-fork global.rb

first pass: more can be removed
Merge pull request #8333 from rolandwalker/strip_some_homebrew_globals

pare back homebrew-fork global.rb
Merge pull request #8332 from rolandwalker/remove_homebrew_misc_methods

remove numerous unused methods from homebrew-fork
Merge pull request #8331 from rolandwalker/remove_homebrew_observer_pathname_extension

remove homebrew-fork module ObserverPathnameExtension
Merge pull request #8329 from rolandwalker/remove_homebrew_mach

remove mach.rb from homebrew-fork
delete homebrew-fork code specific to old Rubies