What's new:
-----------

- Support for CLOCK_REALTIME_COARSE, CLOCK_MONOTONIC_COARSE,
  CLOCK_MONOTONIC_RAW, CLOCK_BOOTTIME, CLOCK_REALTIME_ALARM,
  CLOCK_BOOTTIME_ALARM clocks.

- Support for case sensitive directories.  mkdir(2) automatically
  creates directories within the Cygwin installation dir as case
  sensitive now.

  This feature requires Windows 10 1803 or later and WSL installed!

- New file ioctls's FS_IOC_GETFLAGS and FS_IOC_SETFLAGS.  The actual
  inode flags are Cygwin-specific.  This allows to set or reset
  DOS attributes, file sparseness, FS level encryption and compression,
  as well as directory case sensitivity programatically.

- New tools chattr(1) and lsattr(1) to utilize setting and viewing the
  aforementioned new ioctl's on the command line.

- Support for exFAT.

- Support Linux-specific open(2) flag O_PATH.

- Support Linux-specific linkat(2) flag AT_EMPTY_PATH.

- Support overrun counter for posix timers (via timer_getoverrun() or
  siginfo_t::si_overrun).

- New APIs: signalfd, timerfd_create, timerfd_gettime, timerfd_settime,
  timer_getoverrun.

- fork(2) now is able to recover from when an in-use executable/dll is
  removed or replaced during process runtime.  This feature is disabled by
  default and limited to exes/dlls on the same NTFS partition as the Cygwin
  installation.  For more information and how to enable, please refer to
  https://www.cygwin.com/cygwin-ug-net/highlights.html#ov-hi-process


What changed:
-------------

- clock_nanosleep, pthread_condattr_setclock and timer_create now support
  all clocks, except CLOCK_PROCESS_CPUTIME_ID and CLOCK_THREAD_CPUTIME_ID.

- clock_setres is a no-op now.

- Use the new POSIX unlink semantics on NTFS starting with Windows 10 1709.
  Deleting an in-use file now actually removes the file, rather than moving
  it to the recycler bin.

- Use the new POSIX rename semantics on NTFS starting with Windows 10 1809.
  Renaming a file to another in-use file now actually removes the other file,
  rather than moving it to the recycler bin.

- open(..., O_TMPFILE) now moves the file to the trash bin immediately,
  to free the parent directory.

- Wctype functions updated to Unicode 11.0.

- Remove matherr, and SVID and X/Open math library configurations.
  Default math library configuration is now IEEE.

- Improve uname(2) for newly built applications.

- Kerberos/MSV1_0 S4U authentication replaces two old methods:
  Creating a token from scratch and Cygwin LSA authentication package.

- Cygwin PIDs have been decoupled from Windows PID.  Cygwin PIDs are
  now incrementally dealt in the range from 2 up to 65535, POSIX-like.
  Native Windows processes not started by Cygwin processes are mapped
  into the range beyond 65535.


Bug Fixes
---------

- Fix a thread race when initializing CLOCK_MONOTONIC.
  Addresses: https://cygwin.com/ml/cygwin/2018-11/msg00017.html

- Fix early timeout from pthread_cond_timedwait.
  Addresses: https://cygwin.com/ml/cygwin/2018-11/msg00171.html

- Fix a bug in recognizing remote FAT/FAT32/exFAT correctly.

- Allow open(2)/stat(2)/linkat(2) of a file via /proc/PID/fd/DESCRIPTOR
  even if file has been deleted.
  Addresses: https://cygwin.com/ml/cygwin/2018-12/msg00125.html
             https://cygwin.com/ml/cygwin/2018-12/msg00028.html

- Fix a bug in select(2) when polling HANDLE-less descriptors.

- Fix WEOF handling in wctype functions.
  Addresses: https://cygwin.com/ml/cygwin/2018-12/msg00173.html

- Fix thread names in GDB when cygthreads get reused.

- Fix return value of gethostname in a border case.

- Disallow seteuid on disabled or locked out accounts.
  Addresses: https://cygwin.com/ml/cygwin/2019-01/msg00197.html

- Fix raise to work as required by POSIX.
  Addresses: https://cygwin.com/ml/cygwin/2019-01/msg00149.html

- Fix exception handling in pthreads.
  Addresses: https://cygwin.com/ml/cygwin/2019-01/msg00149.html

- Fix O_APPEND handling on files when calling non-Cygwin applications
  Addresses: https://cygwin.com/ml/cygwin/2019-02/msg00081.html

- Fix case correctness of passwd/group entries fetched via getpwnam
  or getgrnam.
  Addresses: https://cygwin.com/ml/cygwin/2019-02/msg00109.html