Merge pull request
#937 from minrk/readline
Add dirty trick for readline import on OSX to more aggressively detect the presence of libedit masquerading as true GNU readline.
Also made the libedit warning extremely loud, so people don't miss it.
See the original PR page for the gory details; short version:
1. remove lib-dynload from sys.path before trying to import readline the first time
2. after import, restore lib-dynload to its place in sys.path
3. if import failed without lib-dynload, try it one more time, to get the default module
