Programs called by the key handler might replace symlinks instead of their targets.
According to the official [Icon Theme Spec](http://standards.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html#icon_lookup) the Icon key in the desktop entry file should not contain the file extension.
…inted, fixes issue #188
…ed maximum size
Old snprintf calls could have overflowed the buffers.