Bump the CMake version requirement, fix Windows

 - Add a missing runtime library for gettext-tools.
 - Remove the no longer necessary customized FindGettext.cmake,
   since the downloaded gettext binaries are new enough.
 - Make the installer at least ask to uninstall previous versions.
 - Adjust the PATH of tests so that they'll run on Windows directly.
 - Fix quoting so that the project will build inside paths with spaces.
 - Resolve a GSettings deprecation warning.
 - Update the README's build instructions as appropriate.
 - Require CMake 3.9 because of the README's suggestion to fix
   FindPkgConfig.cmake manually using separate_arguments(UNIX_COMMAND).

Tested build configurations:
 - native Arch Linux,
 - native Windows XP with the newest NSIS,
 - Arch Linux Mingw-w64 i686 Win32Depends.cmake NSIS cross-build + XP,
 - Arch Linux Mingw-w64 x86_64 MSYS2 NSIS cross-build + Windows 10.

Detected issues:
 - The file save dialog will not add the extension automatically,
   seen with MSYS2.

0 files changed, 0 insertions, 0 deletions