Add QEMU logo (SVG file)

The "Q" of the logo is already included in pc-bios/qemu_logo_no_text.svg.

This file now adds the complete logo as it was designed by Benoît Canet.
Benoît licensed it under CC-BY 3.0, see
http://lists.gnu.org/archive/html/qemu-devel/2012-02/msg02865.html.

Unneeded borders from Benoît's original logo were removed,
and metadata (license, author, date) was added in this version.

Cc: Benoît Canet <benoit@irqsave.net>
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>