New MLDonkey release 2.7.4

- Use setrlimit to raise allowed ulimit open files
- eMule SUI support (CryptoPP) is now optional, c++ is now an optional dependency
- Fixed bitprint hashing for files > 4GB
- EDK: fixed import_temp command
- EDK: Support for sources in ed2k:// links
example: ed2k://|file|a.txt|1|AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA|/|sources,1.0.0.0:4662|/
- new configure switch: --enable-force-ocaml
Override system-installed Ocaml and force local compile
- Support more system signals: SIGUSR1 saves options, SIGUSR2 performs garbage collection
- code cleaning, removed Redirector, donkeyNeighbours