Changes for version 4.15
- (libev) upgrade to 4.15 - too many changes to list.
- EV::run now returns a boolean.
- API version 5:1.
- document that cleanup watchers are not available via perl.
- cast I32 to int in error message printf.
- remove dependencies on librt and libpthreads on GNU/Linux.
- libev - a high performance full-featured event loop written in C