Fix turbocaching support for Cache-Control max-age
When starting a server with multiple threads, use a single acceptor thread to load balance between threads.

Otherwise, a thread may accept too many clients, leaving little work for other threads to do.
Add an option for specifying the default Ruby interpreter to use
Disable Nagle's algorithm in dev/ruby_server.rb
Fix a bug in installation_utils
Fix compilation errors and warnings
Lower turbocaching threshold to 300

Otherwise, turbocaching won't be triggered when using Rails.
We actually need a better heuristic for enabling turbocaching.
The current heuristic only works if the app is fast enough.