Documentation: Use UTF-8 encoding and fix one wrong encoding

Documentation: Use UTF-8 encoding and fix one wrong encoding

At least for Linux distributions UTF-8 is now standard,
so the QEMU documentation should use this encoding, too.

Even if there was currently only a single special character
using ISO-8859-1, this might change in the future.

So the texinfo keywords @documentlanguage and
@documentencoding now document the language and the
encoding. The special character was changed to UTF-8
(it could also have been changed to an x, but the
original cross looks really nice if it is displayed
correctly).

These changes fix the html presentation at
http://www.qemu.org/qemu-doc.html#SEC65
(ARM System emulator).

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>