Log Message:
Updated npth to 1.4.

Noteworthy changes in version 1.4 (2017-05-16)  [C1/A1/R0]
----------------------------------------------

 * On macOS make use of an unnamed semaphore.

 * Build fixes for FreeBSD, NetBSD, and DragonFlyBSD.

 * New function npth_is_protected to help debugging.

 * Change license from LGPLv3+/GPLv2+ to LGPLv2+.