Localisation support on Windows Visual Studio builds

[jim-easterbrook]

As stated here https://github.com/Exiv2/exiv2#localisation, localisation is not supported on Windows Visual Studio builds. However, it's not too hard to achieve.

First download the gettext executables from http://mlocati.github.io/articles/gettext-iconv-windows.html, unzip the files to any convenient directory, then add their bin directory to your path, e.g.:

set Path=%Path%;C:\gettext0.21-iconv1.16-shared-64\bin

Next add libgettext/0.21 to the requirements method in exiv2's conanfile.py. This provides libintl. There is also a gettext/0.21 conan package with the gettext executables but I couldn't get it to work with exiv2's cmake files. With exiv2 v0.27.7 and earlier you also need to delete cmake\FindIconv.cmake as it prevents use of iconv on Windows.

Now you can run conan and then configure cmake with -D EXIV2_ENABLE_NLS=ON to build libexiv2 with native language support.

In my python-exiv2 project I copy the compiled .mo files into the Python "package data" and call bindtextdomain to get libexiv2 to use them. I don't know how other Windows applications would deal with them.