gnu: icedove-minimal: Add argument to desktop file.
Icedove was not able to handle mailto: links, even if it responded to
them, it only activated the window, but didn't compose a new email.
Calling it directly by `icedove mailto:...` worked. According to:
<https://lists.debian.org/debian-user/2015/06/msg01071.html>
It was missing the argument in the `Exec` line of the desktop file.
* gnu/packages/gnuzilla.scm (icedove-minimal)[phases]
{install-desktop-file}: Add arguments to Exe line in .desktop file.
Change-Id: I3de5e57ed2c5eef23eee88e264487e6460c174b3
Signed-off-by: Efraim Flashner <efraim@flashner.co.il>