Install application icons per Icon Theme Specification

[sebastic]

How to install applications icons as used for the Icon entry in .desktop files is documented in the ​Icon Theme Specification - Installing Application Icons section:

So, you're an application author, and want to install application icons so that they work in the KDE and Gnome menus. Minimally you should install a 48x48 icon in the hicolor theme. This means installing a PNG file in $prefix/share/icons/hicolor/48x48/apps. Optionally you can install icons in different sizes. For example, installing a svg icon in $prefix/share/icons/hicolor/scalable/apps means most desktops will have one icon that works for all sizes. You might even want to install icons with a look that matches other well known themes so your application will fit in with some specific desktop environment.

The attached patch installs the josm icons available in the icons/ directory in /usr/share/icons/hicolor/*/apps following the Icon Theme Specification:

source:  images/logo.svg
testing: linux/tested/usr/share/icons/hicolor/scalable/apps/josm.svg
latest:  linux/latest/usr/share/icons/hicolor/scalable/apps/josm-latest.svg

source:  images/logo_48x48x32.png
testing: linux/tested/usr/share/icons/hicolor/48x48/apps/josm.png
latest:  linux/latest/usr/share/icons/hicolor/48x48/apps/josm-latest.png

source:  images/logo_32x32x32.png
testing: linux/tested/usr/share/icons/hicolor/32x32/apps/josm.png
latest:  linux/latest/usr/share/icons/hicolor/32x32/apps/josm-latest.png

source:  images/logo_16x16x32.png
testing: linux/tested/usr/share/icons/hicolor/16x16/apps/josm.png
latest:  linux/latest/usr/share/icons/hicolor/16x16/apps/josm-latest.png

The PNG icons are installed for old desktops that don't support SVG.

[Don-vip]

In 8845/josm:

fix #11954 - Install application icons per Icon Theme Specification (patch by sebastic)