New calls to select() were introduced into LLDB over the past year that were not doing the right thing on Darwin and these were causing crashes when the file descriptor exceeded FD_SETSIZE. Darwin has special abilities to deal with file descriptors that are greater than or equal to FD_SETSIZE, so we should be able to do things correctly.
This change makes a new File::SelectInfo class that helps encapsulate calls to select() so they all happen correctly. I have updates all calls to select() within LLDB to use this code.
This needs to be tested on Windows, Linux, and FreeBSD. If anyone can't test in the next few days, please resign as reviewer and add someone that can.