This update for libgpiod to version 1.4 fixes the following issues:

* New features:
  - updated the testing framework to work with linux v5.1 in which the debugfs
    interface of the GPIO testing module changed in a backward incompatible way
  - factored out the code controlling the GPIO testing module into a separate
    shared library that may be reused by future testing executables for different
    language bindings
  - removed the --enable-install-tests build option and the make check target as
    they were redundant, subsequently tests are now installed as a normal program
    whenever they're enabled with --enable-tests
* Improvements:
  - removed unnecessary std::move calls from C++ bindings
  - added the explicit keyword to bool() operators in C++ bindings
* Bug fixes:
  - fix out of source build of man pages

This update was imported from the openSUSE:Leap:15.1:Update update project.