Remove dead code
Make this logic less confusing
style
Raise a useful message
Don't use exceptions for flow-control
Remove more dead code
MacSystem now just wraps MacOS
Eliminate MacSystem module
Use MacOS::X11 path helpers
ruby: add mirror

ftp.ruby-lang.org is currently experiencing connectivity issues:
http://www.ruby-lang.org/en/news/2013/08/06/status-issue/

Fixes #21715.
android-sdk: style nits
qt: don't use SSSE3 with superenv.