File Release Notes and Changelog

More bindings, skip missing tests, ability to test features at runtime

* New bindings :
  * getrlimit setrlimit
  * getpriority setpriority
  * ptrace (minimal)
  * renameat mkdirat
  * mlockall munlockall
  * strftime strptime asctime
  * tzname
  * posix_openpt grantpt unlockpt ptsname (Niki Yoshiuchi)
  * getsid
  * ctermid
  * is_open_descr
  * tcgetpgrp tcsetpgrp
  * int_of_file_descr file_descr_of_int
  * sys_exit
* Separate configure test for fsync and fdatasync
* ExtUnix.All.have function to test for features at runtime
* Skip tests of functions not available on the current platform