This patch set updates the platform/unix build system to install all files relevant to file associations and icons.
The first patch installs .desktop and mime-info files. In order to achieve that, I renamed the .desktop file to .desktop.in and used sed substitution to update the install path after configure. The regular CONFIG_STATUS substitution won't work in this case since --bindir may (and usually will) contain variable references.
The second patch installs the program icon. I renamed the icon to love.svg since app.svg is not a suitable 'global namespace' name.
The third patch fixes the Icon= line in the desktop file. That line shall either reference an absolute path to a file, or a basename. In the latter case, Desktop Environment finds the .svg suffix itself.
The fourth patch installs the icon for games. I've renamed it to match the MIME type and therefore make DEs able to find it without overrides.
Finally, the fifth patch updates 'readme.txt' to 'readme.md' in Makefile.am. It therefore fixes make dist.